Communication method considering carrier type and apparatus for same

ABSTRACT

The present invention relates to a method for a terminal, which operates in a half-duplex manner, to communicate with a base station in a wireless communication system supporting a plurality of carrier types, and an apparatus for the same. More particularly, the present invention relates to a method and an apparatus for the same, the method comprising the step of: transmitting a signal to, or receiving a signal from, a base station in a first cell set to be in a time division duplex (TDD) manner via a first subframe positioned between a downlink subframe and an uplink subframe, wherein if the first cell operates as a first carrier type, the first subframe includes a first downlink section, a first protection section, and a first uplink section, and if the first cell operates as a second carrier type, the first subframe includes only a second downlink section and a second protection section, or includes only a second uplink section and the second protection section. The first carrier type represents a carrier type in which a cell-common reference signal is transmitted over the entire system band in all subframes, and the second carrier type represents a carrier type in which the cell-common reference signal is transmitted over at least a part of the system band in some subframes.

This application is a 35 USC §371 National Stage entry of InternationalApplication No. PCT/KR2014/004225 filed on May 12, 2014, and claimspriority to U.S. Provisional Application Nos. 61/822,311 filed on May11, 2013; 61/826,014 filed on May 21, 2013; 61/826,546 filed on May 23,2013; 61/828,178 filed on May 28, 2013; 61/837,148 filed on Jun. 19,2013; 61/839,381 filed on Jun. 26, 2013 and 61/865,154 filed on Aug. 13,2013, all of which are hereby incorporated by reference in theirentireties as if fully set forth herein.

TECHNICAL FIELD

The present invention relates to a wireless communication system. Morespecifically, the present invention relates to a method and apparatusfor configuring a subframe and/or a method and apparatus fortransmitting and receiving a signal in consideration of carrier type.

BACKGROUND ART

Wireless communication systems have been widely deployed to providevarious types of communication services including voice and dataservices. In general, a wireless communication system is a multipleaccess system that supports communication among multiple users bysharing available system resources (e.g. bandwidth, transmit power,etc.) among the multiple users. The multiple access system may adopt amultiple access scheme such as Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), or SingleCarrier Frequency Division Multiple Access (SC-FDMA). In a wirelesscommunication system, a user equipment (UE) can receive information froman eNB on downlink (DL) and transmit information to the eNB on uplink(UL). Information transmitted or received by the UE includes data andvarious types of control information and there are various physicalchannels according to types and purposes of information transmitted orreceived by the UE.

DISCLOSURE Technical Problem

An object of the present invention is to provide an effective subframestructure in a wireless communication system for supporting a pluralityof carrier types.

An object of the present invention is to provide an effective structureof a subframe corresponding to a switching period of downlink and uplinkin a wireless communication system for supporting a plurality of carriertypes.

An object of the present invention is to provide a method and apparatusfor effectively handling collision when uplink and downlink collide in aspecific time period between a plurality cells aggregated in a userequipment (UE) that does not support simultaneous transceivingoperation/capability.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

Technical Solution

In an aspect of the present invention, provided herein is a method forcommunicating with a base station by a user equipment (UE) operating inhalf-duplex in a wireless communication system for supporting aplurality of carrier types, the method comprising: transmitting orreceiving a signal to or from the base station through a first subframelocated between a downlink subframe and an uplink subframe in a firstcell configured in time division duplex (TDD), wherein when the firstcell operates as a first carrier type, the first subframe comprises afirst downlink period, a first guard period, and a first uplink period,wherein when the first cell operates as a second carrier type, the firstsubframe comprises only a second downlink period and a second guardperiod or comprises only a second uplink period or the second guardperiod, and wherein the first carrier type indicates a carrier type inwhich a cell-common reference signal is transmitted over an entiresystem band in all subframes, and the second carrier type indicates acarrier type in which the cell-common reference signal is transmittedover at least part of the system band in some subframes.

In another aspect of the present invention, provided herein is a userequipment (UE) operating in a wireless communication system forsupporting a plurality of carrier types, the UE comprising: a radiofrequency (RF) unit; and a processor, wherein the processor isconfigured to: transmit or receive a signal to or from the base stationthrough a first subframe located between a downlink subframe and anuplink subframe in a first cell configured in time division duplex (TDD)through the RF unit, wherein when the first cell operates as a firstcarrier type, the first subframe comprises a first downlink period, afirst guard period, and a first uplink period, wherein when the firstcell operates as a second carrier type, the first subframe comprisesonly a second downlink period and a second guard period or comprisesonly a second uplink period or the second guard period, and wherein thefirst carrier type indicates a carrier type in which a cell-commonreference signal is transmitted over an entire system band in allsubframes, and the second carrier type indicates a carrier type in whichthe cell-common reference signal is transmitted over at least part ofthe system band in some subframes.

Preferably, when a second cell is additionally aggregated with the firstcell in the UE, and when a link direction of the first cell and a linkdirection of the second cell are different in an at least partial periodof a time period corresponding to the first subframe, transmission orreception of a signal through the second cell is omitted in the at leastpartial period.

Preferably, when a second cell is additionally aggregated with the firstcell in the UE, when the first cell operates as the first carrier typein the first subframe, and when the second cell is configured asdownlink in an at least partial period of a time period corresponding tothe first subframe, a downlink signal is received through the secondcell only in a specific period of the time period.

Preferably, the specific period corresponds to the first downlinkperiod, a downlink period configured in the second cell, a downlinkperiod having a shorter length from among the first cell and the secondcell, or a downlink period having a smaller number of symbols from amongthe first cell and the second cell.

Preferably, when a second cell is additionally aggregated with the firstcell in the UE, when the first cell operates as the first carrier typein the first subframe, and when the second cell is configured as uplinkin a time period corresponding to the first subframe, transmission of aphysical uplink shared channel signal or a physical uplink controlchannel signal through the second cell is omitted in the time period.

Preferably, when a second cell is additionally aggregated with the firstcell in the UE, when the first cell operates as the second carrier typeand the second cell operates as the first carrier type in a time periodcorresponding to the first subframe, when the first subframe comprisesonly the second downlink period and the second guard period, and whenthe second cell is configured as downlink in the time period, detectionor reception a physical downlink shared channel, a physical downlinkcontrol channel mapped over a data region of a subframe, a physicalmulticast channel, and a positioning reference signal is omitted in thetime period.

Preferably, when a second cell is additionally aggregated with the firstcell in the UE, when the first cell operates as the second carrier typeand the second cell operates as the first carrier type in a time periodcorresponding to the first subframe, when the first subframe comprisesonly the second downlink period and the second guard period, and whenthe second cell is configured as uplink in the time period, transmissionof a physical uplink shared channel and a physical uplink controlchannel is omitted in the time period.

Preferably, a length of the second uplink period is increased by alength of the first downlink period as compared to a length of the firstuplink period, and a length of the second downlink period is increasedby a length of the first uplink period as compared to a length of thefirst downlink period.

Advantageous Effects

A subframe structure according to the present invention may enhanceefficiency in a wireless communication system for supporting a pluralityof carrier types.

A subframe structure according to the present invention may effectivelytransmit and receive a signal in a switching period of downlink anduplink in a wireless communication system for supporting a plurality ofcarrier types.

In addition, the present invention may effectively handle collision whenuplink and downlink collide in a specific time period between aplurality cells aggregated in a user equipment (UE) that does notsupport simultaneous transceiving operation/capability.

It will be appreciated by persons skilled in the art that that theeffects that could be achieved with the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood fromthe following detailed description taken in conjunction with theaccompanying drawings.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

In the drawings:

FIG. 1 illustrates a structure of a radio frame.

FIG. 2 illustrates a resource grid of one downlink slot.

FIG. 3 illustrates physical channels used in LTE(-A) and a signaltransmission method using the same.

FIG. 4 illustrates a primary broadcast channel (P-BCH) and asynchronization channel (SCH).

FIG. 5 illustrates a downlink subframe structure.

FIG. 6 illustrates a control channel allocated to a downlink subframe.

FIG. 7 illustrates a configuration of a demodulation reference signal(DM-RS) configuration added to LTE-A.

FIG. 8 illustrates a structure of an uplink subframe.

FIGS. 9 and 10 illustrate a carrier aggregation (CA) communicationsystem.

FIG. 11 illustrates exemplary subframe structures of LCT and NCT.

FIG. 12 illustrates an example in which a DL physical channel isallocated to a subframe.

FIG. 13 illustrates an example of the numbers of OFDM symbols in adownlink period, a guard period, and an uplink period according to aspecial subframe configuration.

FIG. 14 illustrates an example of a DM-RS configuration according to thepresent invention.

FIG. 15 illustrates collision of subframes in different cells.

FIG. 16 illustrates an example of a special subframe configuration.

FIG. 17 illustrates a base station and a user equipment to which thepresent invention is applicable.

BEST MODE

Embodiments of the present invention are applicable to a variety ofwireless access technologies such as Code Division Multiple Access(CDMA), Frequency Division Multiple Access (FDMA), Time DivisionMultiple Access (TDMA), Orthogonal Frequency Division Multiple Access(OFDMA), and Single Carrier Frequency Division Multiple Access(SC-FDMA). CDMA can be implemented as a radio technology such asUniversal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can beimplemented as a radio technology such as Global System for Mobilecommunications (GSM)/General Packet Radio Service (GPRS)/Enhanced DataRates for GSM Evolution (EDGE). OFDMA can be implemented as a radiotechnology such as Institute of Electrical and Electronics Engineers(IEEE) 802.11 (Wireless Fidelity (Wi-Fi)), IEEE 802.16 (Worldwideinteroperability for Microwave Access (WiMAX)), IEEE 802.20, and EvolvedUTRA (E-UTRA). UTRA is a part of Universal Mobile TelecommunicationsSystem (UMTS). 3^(rd) Generation Partnership Project (3GPP) Long TermEvolution (LTE) is a part of Evolved UMTS (E-UMTS) using E-UTRA,employing OFDMA for downlink and SC-FDMA for uplink. LTE-Advanced(LTE-A) is evolved from 3GPP LTE.

For clarity of explanations, the following description focuses on 3GPPLTE(-A) system. However, technical features of the present invention arenot limited thereto. Further, a particular terminology is provided forbetter understanding of the present invention. However, such aparticular terminology may be changed without departing from thetechnical spirit of the present invention. For example, the presentinvention may be applied to a system in accordance with a 3GPP LTE/LTE-Asystem as well as a system in accordance with another 3GPP standard,IEEE 802.xx standard, or 3GPP2 standard.

In the present specification, a user equipment (UE) may be a fixedstation or a mobile station, and the UE may be one of various equipmentstransmitting and receiving data and/or control information bycommunicating with a base station (BS). The UE may be referred to as aterminal, a mobile station (MS), a mobile terminal (MT), a user terminal(UT), a subscriber station (SS), a wireless device, a personal digitalassistant (PDA), a wireless modem, a handheld device, and etc. In thepresent specification, the term “UE” may be interchangeably used withthe term “terminal”.

In the present specification, a base station (BS) may be a fixed stationcommunicating with a UE and/or another BS in general, but may refer to amobile station in some systems. The BS exchanges data and controlinformation by communicating with a UE and another BS. A base station(BS) may be referred to as an advanced base station (ABS), a node-B(NB), an evolved nodeB (eNB), a base transceiver system (BTS), an accesspoint, a processing server (PS), a node, a transmission point (TP), andetc. In the present specification, a base station (BS) may beinterchangeably used with eNB. Further, in a system supporting a smallcell or a device-to-device communication, a base station may representthe small cell or a cluster header UE, respectively.

FIG. 1 illustrates a structure of a radio frame used in the LTE(-A)system. Uplink/downlink data packet transmission is performed in theunit of a subframe (SF), and one subframe is defined as a time intervalincluding a plurality of symbols. The 3PP LTE system supports a type-1radio frame structure applicable to frequency division duplex (FDD) anda type-2 radio frame structure applicable to time division duplex (TDD).

FIG. 1(a) illustrates the structure of the type-1 radio frame. Adownlink radio frame includes 10 subframes and one subframe includes twoslots in a time domain. A time required to transmit one subframe isreferred to as a transmission time interval (TTI). For example, onesubframe has a length of 1 ms and one slot has a length of 0.5 ms. Oneslot includes a plurality of OFDM symbols in a time domain and includesa plurality of resource blocks (RBs) in a frequency domain. In the 3GPPLTE system, since OFDM is used in downlink, an OFDM symbol indicates onesymbol period. An OFDM symbol may be referred to as an SC-FDMA symbol inthe present specification, and also may be referred to as a symbolperiod. A resource block (RB) as a resource assignment unit may includea plurality of consecutive subcarriers in one slot.

The number of OFDM symbols included in one slot may vary according to aconfiguration of cyclic prefix (CP). The cyclic prefix includes anextended CP and a normal CP. For example, if OFDM symbols are configuredby the normal CP, the number of OFDM symbols included in one slot may be7. In case that an OFDM symbol is configured with an extended CP, alength of one OFDM symbol is larger, so that the number of OFDM symbolsincluded in one slot is fewer than that of normal CP. In case of theextended CP, for example, the number of OFDM symbols included in oneslot may be 6. When a channel status is not stable such as a UE movingin a high speed, an extended CP may be used to reduce an inter-symbolinterference.

In the case that a normal CP is used, since a slot includes 7 OFDMsymbols, a subframe includes 14 OFDM symbols. A maximum of initial 3OFDM symbols may be allocated to a physical downlink control channel(PDCCH), and remaining OFDM symbols may be allocated to a physicaldownlink shared channel (PDSCH).

FIG. 1(b) illustrates a structure of the type-2 radio frame. The type-2radio frame includes two half frames, and each half frame includes four(or five) normal subframes and one (or zero) special subframe. A normalsubframe is used for uplink or downlink according to an uplink-downlink(UL-DL) configuration. One subframe includes two slots.

Table 1 shows an example of an uplink-downlink (UL-DL) configuration ofsubframes within a radio frame in a TDD mode.

TABLE 1 Uplink-downlink Downlink-to-Uplink Subframe number configurationSwitch-point periodicity 0 1 2 3 4 5 6 7 8 9 0  5 ms D S U U U D S U U U1  5 ms D S U U D D S U U D 2  5 ms D S U D D D S U D D 3 10 ms D S U UU D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D D D D 6  5ms D S U U U D S U U D

In Table 1 above, D represents a downlink subframe (DL SF), U representsan uplink subframe (UL SF), and S represents a special subframe. Thespecial subframe includes a downlink period, a guard period (GP), and anuplink period. Table 2 shows an example of a special subframeconfiguration. The downlink period may be referred to as a downlinkpilot time slot (DwPTS), and the DwPTS is used for an initial cellsearch, synchronization, or channel estimation at a UE. The uplinkperiod may be referred to as an uplink pilot time slot (UpPTS), and theUpPTS is used for a channel estimation and adjusting uplink transmissionsynchronization of a UE at a base station. The guard period is used toeliminate interference generated in uplink due to multi-path delay of adownlink signal between uplink and downlink.

In the case of a TDD-based LTE(-A) system, as illustrated in FIG. 1(b),a timing gap is required for the transition from a DL subframe to an ULsubframe, and to this end a special subframe is included between a DL SFand a UL SF. The special SF may have various configuration according toradio condition, a location of a UE and etc. DwPTS/GP/UpPTS may bevariously configured according to special subframe (SF) configuration.Table 2 illustrates a special subframe configuration.

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Normal Extended Normal Extended Special subframecyclic prefix cyclic prefix cyclic prefix cyclic prefix configurationDwPTS in uplink in uplink DwPTS in uplink in uplink 0  6592 · T_(s) 2192· T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 ·T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600· T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592· T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 ·T_(s) 7 21952 · T_(s) — — — 8 24144 · T_(s) — — —

The above-described radio frame structure is exemplary. Thus, the numberof subframes in a radio frame, the number of slots in a subframe, or thenumber of symbols in a slot may be modified in various ways.

FIG. 2 illustrates a resource grid of one downlink slot.

Referring to FIG. 2, a downlink slot includes a plurality of OFDMsymbols in the time domain. One downlink slot may include 7 (or 6) OFDMsymbols and include a plurality of resource blocks (RBs). One resourceblock (RB) may include 12 subcarriers in the frequency domain. Eachelement of the resource grid is referred to as a Resource Element (RE).An RB includes 12×7 (or 6) REs. The number of RBs in a downlink slot,N_(DL), depends on a downlink transmission bandwidth. The structure ofan uplink slot may have the same structure as a downlink slot, but anOFDM symbol is replaced by an SC-FDMA symbol.

FIG. 3 illustrates physical channels used in LTE(-A) and a signaltransmission method using the same.

Referring to FIG. 3, when powered on or when a UE initially enters acell, the UE performs initial cell search involving synchronization witha BS in step S101. For initial cell search, the UE synchronizes with theBS and acquire information such as a cell Identifier (ID) by receiving aprimary synchronization channel (P-SCH) and a secondary synchronizationchannel (S-SCH) from the BS. Then the UE may receive broadcastinformation from the cell on a physical broadcast channel (PBCH). In themean time, the UE may check a downlink channel status by receiving adownlink reference signal (DL RS) during initial cell search.

After initial cell search, the UE may acquire more specific systeminformation by receiving a physical downlink control channel (PDCCH) andreceiving a physical downlink shared channel (PDSCH) based oninformation of the PDCCH in step S102.

The UE may perform a random access procedure to access the BS in stepsS103 to S106. For random access, the UE may transmit a preamble to theBS on a physical random access channel (PRACH) (S103) and receive aresponse message for preamble on a PDCCH and a PDSCH corresponding tothe PDCCH (S104). In the case of contention-based random access, the UEmay perform a contention resolution procedure by further transmittingthe PRACH (S105) and receiving a PDCCH and a PDSCH corresponding to thePDCCH (S106).

After the foregoing procedure, the UE may receive a PDCCH/PDSCH (S107)and transmit a physical uplink shared channel (PUSCH)/physical uplinkcontrol channel (PUCCH) (S108), as a general downlink/uplink signaltransmission procedure. Here, control information transmitted from theUE to the BS is called uplink control information (UCI). The UCI mayinclude a hybrid automatic repeat and request (HARQ) acknowledgement(ACK)/negative-ACK (HARQ ACK/NACK) signal, a scheduling request (SR),channel state information (CSI), etc. The CSI includes a channel qualityindicator (CQI), a precoding matrix index (PMI), a rank indicator (RI),etc. While the UCI is transmitted through a PUCCH in general, it may betransmitted through a PUSCH when control information and traffic dataneed to be simultaneously transmitted. The UCI may be aperiodicallytransmitted through a PUSCH at the request/instruction of a network.

FIG. 4 illustrates a primary broadcast channel (P-BCH) and asynchronization channel (SCH). The SCH includes a P-SCH and an S-SCH.The P-SCH carries a primary synchronization signal (PSS) and the S-SCHcarries a secondary synchronization signal (SSS).

Referring to FIG. 4, in frame configuration type-1 (FDD), the P-SCH islocated in the last OFDM symbols of slot #0 (i.e. the first slot ofsubframe #0) and slot #10 (i.e. the first slot of subframe #5) in eachradio frame. The S-SCH is located OFDM symbols immediately before thelast OFDM symbols of slot #0 and Slot #10. The S-SCH and P-SCH aredisposed in consecutive OFDM symbols. In frame configuration type-2(TDD), the P-SCH is transmitted through the third OFDM symbol ofsubframe #1/#6 and the S-SCH is located in the last OFDM symbols of slot#1 (i.e. the second slot of subframe #0) and slot #11 (i.e. the secondslot of subframe #5). The P-SCH is transmitted for every 4 radio framesirrespective of frame configuration type using the first to fourth OFDMsymbols of the second slot of subframe #0. The P-SCH is transmittedusing 72 subcarriers (10 subcarriers are reserved and 62 subcarriers areused for PSS transmission) on the basis of direct current (DC)subcarriers in OFDM symbols. The S-SCH is transmitted using 72subcarriers (10 subcarriers are reserved and 62 subcarriers are used forSSS transmission) on the basis of DC subcarriers in OFDM symbols. TheP-BCH is mapped to 72 subcarriers on the basis of 4 OFDM symbols and DCsubcarriers in one subframe.

FIG. 5 illustrates a downlink subframe structure.

Referring to FIG. 5, a maximum of 3 (4) OFDM symbols located in a frontportion of a first slot within a subframe correspond to a control regionto which a control channel is allocated. The remaining OFDM symbolscorrespond to a data region to which a physical downlink shared chancel(PDSCH) is allocated. Examples of downlink control channels used in LTEinclude a physical control format indicator channel (PCFICH), a physicaldownlink control channel (PDCCH), a physical hybrid ARQ indicatorchannel (PHICH), etc.

FIG. 6 illustrates a control channel allocated to a downlink subframe.In FIG. 6, R1 to R4 represent CRSs (Cell-specific Reference Signals orCell-common Reference Signals) for antenna ports 0 to 3. A CRS istransmitted per subframe in total-band and fixed to a specific patternin a subframe. The CRS is used for channel measurement and downlinksignal demodulation.

Referring to FIG. 6, a PCFICH is transmitted at the first OFDM symbol ofa subframe and carries information regarding the number of OFDM symbolsused for transmission of control channels within the subframe. ThePCFICH is composed of 4 REGs which are equally distributed in thecontrol region on the basis of cell ID. The PCFICH indicates values of 1to 3 (or 2 to 4) and is modulated according to QPSK (Quadrature PhaseShift Keying). The PHICH is a response of uplink transmission andcarries an HARQ acknowledgment (ACK)/negative-acknowledgment (NACK)signal. The PHICH is allocated to REGs except CRS and PCFICH (the firstOFDM symbol) in one or more OFDM symbols set based on PHICH duration.The PHICH is allocated to 3 REGs distributed in the frequency domain.

A PDCCH is allocated to the first n OFDM symbols (referred to as acontrol region hereinafter) of a subframe. Here, n is an integer equalto or greater than 1 and is indicated by a PCFICH. Control informationtransmitted through a PDCCH is referred to as DCI. Formats 0, 3, 3A and4 for uplink and formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B and 2C fordownlink are defined as DCI formats. Information field types, the numberof information fields and the number of bits of each information fielddepend on DCI format. For example, the DCI formats selectively includeinformation such as hopping flag, RB allocation, MCS (modulation codingscheme), RV (redundancy version), NDI (new data indicator), TPC(transmit power control), HARQ process number, PMI (precoding matrixindicator) confirmation as necessary.

The PDCCH may carry a transport format and a resource allocation of adownlink shared channel (DL-SCH), resource allocation information of anuplink shared channel (UL-SCH), paging information on a paging channel(PCH), system information on the DL-SCH, information on resourceallocation of an upper-layer control message such as a random accessresponse transmitted on the PDSCH, a set of Tx power control commands onindividual UEs within an arbitrary UE group, a Tx power control command,information on activation of a voice over IP (VoIP), etc. A plurality ofPDCCHs can be transmitted within a control region. The UE can monitorthe plurality of PDCCHs. The PDCCH is transmitted on an aggregation ofone or several consecutive control channel elements (CCEs). The CCE is alogical allocation unit used to provide the PDCCH with a coding ratebased on a state of a radio channel. The CCE corresponds to a pluralityof resource element groups (REGs). A format of the PDCCH and the numberof bits of the available PDCCH are determined by the number of CCEs. TheBS determines a PDCCH format according to DCI to be transmitted to theUE, and attaches a cyclic redundancy check (CRC) to control information.The CRC is masked with a unique identifier (referred to as a radionetwork temporary identifier (RNTI)) according to an owner or usage ofthe PDCCH. If the PDCCH is for a specific UE, a unique identifier (e.g.,cell-RNTI (C-RNTI)) of the UE may be masked to the CRC. Alternatively,if the PDCCH is for a paging message, a paging identifier (e.g.,paging-RNTI (P-RNTI)) may be masked to the CRC. If the PDCCH is forsystem information (more specifically, a system information block(SIB)), a system information RNTI (SI-RNTI) may be masked to the CRC.When the PDCCH is for a random access response, a random access-RNTI(RA-RNTI) may be masked to the CRC.

A plurality of PDCCHs can be transmitted in a subframe. Each PDCCH istransmitted using one or more CCEs each of which corresponds to 9 setsof 4 REs. 4 REs are referred to as a resource element group (REG). 4QPSK symbols are mapped to an REG. An RE allocated to a reference signalis not included in an REG and thus the number of REGs in an OFDM symboldepends on presence or absence of a cell-specific reference signal.

Table 3 shows the number of CCEs, the number of REGs and the number ofPDCCH bits according to PDCCH format.

TABLE 3 PDCCH Number of PDCCH format Number of CCE (n) Number of REGbits 0 1 9 72 1 2 18 144 2 4 36 288 3 8 72 576

CCEs are sequentially numbered. To simplify decoding, transmission of aPDCCH having a format composed of n CCEs can be started using a multipleof n CCEs. The number of CCEs used to transmit a specific PDCCH isdetermined by a BS according to channel quality. For example, in case ofa PDCCH assigned to a UE having a high-quality downlink channel (e.g. achannel close to the BS), only one CCE can be used to transmit thePDCCH. However, in the case of a PDCCH assigned to a UE having a poorchannel state (e.g. close to a cell edge), 8 CCEs can be used for PDCCHtransmission in order to obtain sufficient robustness. In addition, apower level of the PDCCH can be controlled according to channel quality.

In LTE(-A), positions of CCEs in a limited set in which a PDCCH can bedisposed for each UE are defined. The positions of CCEs in a limited setin which a UE can detect a PDCCH allocated thereto are referred to asthe “search space (SS)”. In LTE(-A), the size of the search spacedepends upon the PDCCH format. In addition, UE-specific and commonsearch spaces are separately defined. The UE-specific search space (USS)is set on a UE basis, whereas the common search space (CSS) is known toall UEs. The USS and CSS may overlap. If a UE has a considerably smallsearch space, no CCE is left when CCEs are allocated in the searchspace. Accordingly, a BS may not detect CCEs through which a PDCCH willbe transmitted to the UE in a predetermined subframe, which is referredto as blocking. To minimize possibility that blocking continues in thenext subframe, the start point of the USS is hopped in a UE-specificmanner.

Sizes of the CSS and USS are shown in Table 4.

TABLE 4 Number of CCE Number of Number of PDCCH format (n) candidates inCSS candidates in USS 0 1 — 6 1 2 — 6 2 4 4 2 3 8 2 2

To control computational load of blind decoding based on the number ofblind decoding processes, a UE is not required to simultaneously searchfor all defined DCI formats. In general, the UE searches for formats 0and 1A at all times in the USS. Formats 0 and 1A have the same size andare discriminated from each other by a flag in a message. The UE mayneed to receive an additional format (e.g. format 1, 1B or 2 accordingto PDSCH transmission mode set by a BS). The UE searches for formats 1Aand 1C in the CSS. Furthermore, the UE may be set to search for format 3or 3A. Formats 3 and 3A have the same size as formats 0 and 1A and maybe discriminated from each other by scrambling CRC with different(common) identifiers rather than a UE-specific identifier. PDSCHtransmission schemes according to transmission mode and informationcontent of DCI formats are arranged in the following.

Transmission Mode (TM)

-   -   Transmission mode 1: Transmission from a single BS antenna port    -   Transmission mode 1: Transmission from a single BS antenna port    -   Transmission mode 3: Open-loop spatial multiplexing    -   Transmission mode 4: Closed-loop spatial multiplexing    -   Transmission mode 5: Multi-user MIMO    -   Transmission mode 6: Closed-loop rank-1 precoding    -   Transmission mode 7: Single-antenna port (port 5) transmission    -   Transmission mode 8: Double layer transmission (ports 7 and 8)        or single-antenna port (port 7 or 8) transmission    -   Transmission modes 9 and 10: Up to 8 layer transmission (ports 7        to 14) or single-antenna port (port 7 or 8) transmission.

DCI Format

-   -   Format 0: Resource grants for the PUSCH transmissions (uplink)    -   Format 1: Resource assignments for single codeword PDSCH        transmissions (transmission modes 1, 2 and 7)    -   Format 1A: Compact signaling of resource assignments for single        codeword PDSCH (all modes)    -   Format 1B: Compact resource assignments for PDSCH using rank-1        closed loop precoding (mode 6)    -   Format 1C: Very compact resource assignments for PDSCH (e.g.        paging/broadcast system information)    -   Format 1D: Compact resource assignments for PDSCH using        multi-user MIMO (mode 5)    -   Format 2: Resource assignments for PDSCH for closed-loop MIMO        operation (mode 4)    -   Format 2A: Resource assignments for PDSCH for open-loop MIMO        operation (mode 3)    -   Format 3/3A: Power control commands for PUCCH and PUSCH with        2-bit/1-bit power adjustments    -   Format 4: Resource grants for PUSCH transmission (uplink) in a        cell set to multi-antenna port transmission mode

DCI formats can be classified into a TM-dedicated format and a TM-commonformat. The TM-dedicated format refers to a DCI format set to acorresponding TM only and the TM-common format refers to a DCI formatset to all TMs. For example, DCI format 2B is a TM-dedicated DCI formatin the case of TM 8, DCI format 2C is a TM-dedicated DCI format in thecase of TM 9 and DCI format 2D is a TM-dedicated DCI format in the caseof TM 10. DCI format 1A may be a TM-common DCI.

In the mean time, in a long term evolution-advanced (LTE-A) system, amultimedia broadcast multicast service single frequency network(MBSFN)-based multimedia broadcast and multimedia service (MBMS) isdefined in order to provide a broadcast service over a communicationnetwork. An MBSFN is technology for simultaneously transmitting the samedata at the same time in all of nodes belonging to an MBSFN area insynchronization with a radio resource. Here, the MBSFN area refers to anarea covered by one MBSFN. According to the MBSFN, even when the UE islocated at an edge of coverage of a node that the UE has accessed, asignal of a neighboring node functions not as interference but as gain.That is, the MBSFN introduces a single frequency network (SFN) functionfor MBMS transmission, thereby reducing service interference caused byfrequency switching in the middle of MBMS transmission. Therefore, theUE within the MBSFN area recognizes MBMS data transmitted by multiplenodes as data transmitted by one node and in this MBSFN area, the UE mayreceive a seamless broadcast service without an additional handoverprocedure even while in motion. In the MBSFN, since a plurality of nodesuse a single frequency in order to simultaneously perform synchronizedtransmission, frequency resources can be saved and spectrum efficiencycan be raised. The UE can receives a higher-layer signal notifying anMBSFN subframe, thereby knowing which subframe is reserved for MBSFN. Asubframe reserved for MBSFN in downlink may be referred to as an MBSFNsubframe.

Meanwhile, when a packet is transmitted in a wireless communicationsystem, signal distortion may occur during transmission since the signalis transmitted through a radio channel. To correctly receive a distortedsignal at a receiver, the distorted signal needs to be corrected usingchannel information. To detect channel information, a signal known toboth a transmitter and the receiver is transmitted and channelinformation is detected with a degree of distortion of the signal whenthe signal is received through a channel. This signal is referred to asa pilot signal or a reference signal.

Reference signals may be classified into a reference signal foracquiring channel information and a reference signal used for datademodulation. The former is for a UE to acquire channel information indownlink, the reference signal for acquiring channel information istransmitted in wideband, and a UE which does not receive downlink datain a specific subframe receives the reference signal. Further, thisreference signal is used in a handover situation. The latter is areference signal transmitted together when a base station transmits adownlink signal, and enables a UE to demodulate the downlink signalusing the reference signal. The reference signal used for datademodulation is required to be transmitted in a data transmissionregion.

Downlink reference signal includes: i) a cell-specific reference signal(CRS) shared by all UEs in a cell; ii) a UE-specific reference signalfor a specific UE only; iii) a demodulation reference signal (DM-RS)transmitted for coherent demodulation when a PDSCH is transmitted; iv) achannel state information reference signal (CSI-RS) for deliveringchannel state information (CSI) when a downlink DMRS is transmitted; v)a multimedia broadcast single frequency network (MBSFN) reference signaltransmitted for coherent demodulation of a signal transmitted in MBSFNmode; and vi) a positioning reference signal used to estimate geographicposition information of a UE.

FIG. 7 illustrates a configuration of a demodulation reference signal(DM-RS) configuration added to LTE-A. A DM-RS is a UE-specific RS usedto demodulate a signal of each layer when signals are transmitted usingmultiple antennas. Since LTE-A considers a maximum of 8 transmitantennas, a maximum of 8 layers and respective DM-RSs therefor areneeded.

Referring to FIG. 7, two or more layers share the same RE and DM-RS ismultiplexed according to CDM (Code Division Multiplexing). Specifically,DM-RSs for respective layers are spread using a spreading code (e.g. anorthogonal code such as a Walsh code or a DFT code) and then multiplexedto the same RE. For example, DM-RSs for layers 0 and 1 share the same REand are spread on 2 REs of OFDM symbols 12 and 13 using an orthogonalcode. That is, in each slot, the DM-RSs for layers 0 and 1 are spreadusing a code with SF (Spreading Factor)=2 in the time domain and thenmultiplexed to the same RE. For example, the DM-RS for layer 0 can bespread using [+1 +1] and the DM-RS for layer 1 can be spread using [+1−1]. Similarly, DM-RSs for layers 2 and 3 are spread on the same REsusing different orthogonal codes. DM-RSs for layers 4, 5, 6 and 7 arespread on REs occupied by DM-RSs 0, 1, 2 and 3 using a code orthogonalto layers 0, 1, 2 and 3. A code with SF=2 is used for DM-RS for up to 4layers and a code with SF=4 is used for DM-RSs when five or more layersare used. Antenna ports for DM-RSs are {7, 8, . . . , n+6}(n being thenumber of layers).

Table 5 shows spreading sequences for antenna ports 7 to 14 defined inLTE-A.

TABLE 5 Antenna port p [w _(p)(0) w _(p)(1) w _(p)(2) w _(p)(3)] 7 [+1+1 +1 +1] 8 [+1 −1 +1 −1] 9 [+1 +1 +1 +1] 10 [+1 −1 +1 −1] 11 [+1 +1 −1−1] 12 [−1 −1 +1 +1] 13 [+1 −1 −1 +1] 14 [−1 +1 +1 −1]

Referring to Table 5, orthogonal codes for antenna ports 7 to 10 have astructure in which a length-2 orthogonal code is repeated. Accordingly,a length-2 orthogonal code is used at the slot level for up to 4 layersand a length-4 orthogonal code is used at the subframe level when fiveor more layers are used.

FIG. 8 illustrates a structure of an uplink subframe.

Referring to FIG. 8, the uplink subframe includes a plurality of slots(for example, two). Each slot may include a plurality of SC-FDMAsymbols, wherein the number of SC-FDMA symbols included in each slot isvaried depending on a cyclic prefix (CP) length. In an example, a slotmay comprise 7 SC-FDMA symbols in case of normal CP, and a slot maycomprise 6 SC-FDMA symbols in case of extended CP. An uplink subframe isdivided into a data region and a control region. The data regionincludes a PUSCH, and is used to transmit a data signal that includesvoice information. The control region includes a PUCCH, and is used totransmit uplink control information (UCI). The PUCCH includes RB pair(e.g. m=0, 1, 2, 3) located at both ends of the data region on afrequency axis (e.g. RB pair located frequency mirrored positions), andperforms hopping on the border of the slots. The uplink controlinformation (UCI) includes HARQ ACK/NACK, CQI (Channel QualityIndicator), a precoding matrix indicator (PMI), a rank indicator (RI),etc.

The LTE system supports a sounding reference signal (SRS) a demodulationreference signal (DMRS) as an uplink reference signal. The demodulationreference signal may be combined with a transmission of PUSCH or PUCCH,and may be transmitted by a UE to a base station for demodulation of anuplink signal. The sounding reference signal may be transmitted by a UEto a base station for uplink scheduling. The base station estimate anuplink channel using the received sounding reference signal and uses theestimated uplink channel for uplink scheduling. The sounding referencesignal is not combined with a transmission of PUSCH or PUCCH. The sametype of base sequence may be used for the demodulation reference signaland the sounding reference signal.

FIG. 9 illustrates a carrier aggregation (CA) communication system.

Referring to FIG. 9, a plurality of uplink/downlink component carriers(CCs) can be aggregated to support a wider uplink/downlink bandwidth. Assuch, a technique of aggregating and using the plurality ofuplink/downlink component carriers is referred to as a carrieraggregation or bandwidth aggregation. A component carrier may beunderstood as a carrier frequency (or center carrier, center frequency)for a corresponding frequency block. The CCs may be contiguous ornon-contiguous in the frequency domain. Bandwidths of the CCs can beindependently determined. Asymmetrical CA in which the number of UL CCsis different from the number of DL CCs can be implemented. A linkbetween DL CC and UL CC may be fixed in a system or may besemi-statically configured. Further, even if the entire system bandwidthcomprises N CCs, a bandwidth used for monitoring/receiving by a specificUE may be limited to M(<N) CCs. Various parameters for carrieraggregation may be configured in a cell-specific, or UE group-specific,or UE-specific manner.

Control information may be transmitted/received only through a specificCC. This specific CC may be referred to as a primary CC (PCC) and theother CC may be referred to as a secondary CC (SCC). PCC may be used forperforming an initial connection establishment procedure or connectionre-establishment procedure. PCC may refer to a cell indicated during ahandover procedure. SCC may be configurable after an RRC connectionestablishment and may be used for providing additional radio resources.In an example, scheduling information may be configured to betransmitted and received through a specific CC only, and such ascheduling scheme is referred to as a cross-carrier scheduling (orcross-CC scheduling). When cross-carrier scheduling (or cross-CCscheduling) is applied, a PDCCH for downlink allocation can betransmitted through DL CC#0 and a PDSCH corresponding to the PDCCH canbe transmitted through DL CC#2. The term “component carrier” can bereplaced by other equivalent terms (e.g. carrier, cell, etc.). Forexample, PCC and SCC may be interchangeably used with PCell and SCell,respectively. Further, the initial connection establishment proceduremay be performed on PCell, and SCell may be additionally aggregated asneeded.

For cross-CC scheduling, a carrier indicator field (CIF) is used.Presence or absence of the CIF in a PDCCH can be determined by higherlayer signaling (e.g. RRC signaling) semi-statically and UE-specifically(or UE group-specifically). The baseline of PDCCH transmission issummarized as follows.

-   -   CIF disabled: a PDCCH on a DL CC is used to allocate a PDSCH        resource on the same DL CC or a PUSCH resource on a linked UL        CC.    -   No CIF    -   CIF enabled: a PDCCH on a DL CC can be used to allocate a PDSCH        or PUSCH resource on a specific DL/UL CC from among a plurality        of aggregated DL/UL CCs using the CIF.    -   LTE DCI format extended to have the CIF    -   CIF corresponds to a fixed x-bit field (e.g. x=3) (when the CIF        is set).    -   CIF position is fixed irrespective of DCI format size (when the        CIF is set).

When the CIF is present, the BS can allocate a PDCCH monitoring DL CC(set) to reduce BD complexity of the UE. For PDSCH/PUSCH scheduling, aUE can detect/decode a PDCCH only in the corresponding DL CC. The BS cantransmit the PDCCH only through the monitoring DL CC (set). Themonitoring DL CC set can be set UE-specifically, UE-group-specificallyor cell-specifically.

FIG. 10 illustrates a case in which 3 DL CCs are aggregated and DL CC Ais set to a monitoring DL CC. When the CIF is disabled, each DL CC cancarry a PDCCH that schedules a PDSCH of the DL CC without the CIFaccording to LTE PDCCH rules. When the CIF is enabled through higherlayer signaling, DL CC A can carry not only a PDSCH thereof but alsoPDSCHs of other DL CCs using the CIF. DL CC B and DL CC C which are notset to monitoring DL CCs do not carry a PDCCH. Here, the term“monitoring DL CC” can be used interchangeably with terms such as“monitoring carrier”, “monitoring cell”. “scheduling carrier”,“scheduling cell”, “serving carrier”, “serving cell”, etc. A DL CC onwhich a PDSCH corresponding to a PDCCH is transmitted and a UL CC onwhich a PUSCH corresponding to a PUCCH is transmitted are referred to asa scheduled carrier, a scheduled cell, etc.

In an LTE Release-8/9/10 system, a CRS may be transmitted through all DLsubframes except for a DL subframe configured for a specific purpose(e.g., a MBSFN subframe) with respect to an arbitrary carrier. Inaddition, a control channel such as PCFICH/PDCCH/PHICH may betransmitted across the first some OFDM symbol(s) of all DL subframes. Assuch, in the LTE Release-8/9/10 system, backward compatibility forproviding access and services of an existing UE may be ensured. On theother hand, a next system may introduce a new type of carrier in whichall or some of the aforementioned backward compatible legacysignals/channels are not transmitted because an issue in terms ofinterference between a plurality of cells can be overcome, carrierexpansion is enhanced, and a freedom degree for providing advancedfeature (e.g., 8Tx MIMO). In the present invention, for convenience, thenew type of carrier is defined as a new carrier type (NCT). Compared tothis, a carrier type according to legacy 3GPP LTE Release-8/9/10 isreferred to as a legacy carrier type (LCT).

In the NCT, basically, transmission of a fixed CRS with high density maybe omitted or remarkably reduced. That is, in the NCT, DL data receptionand channel state measurement dependent upon CRS transmission may beomitted or remarkably reduced. Instead, DL reception performance may beenhanced and RS overhead may be minimized by receiving DL data based ona DM-RS that is UE-specifically (precoded) and transmitted and measuringa channel state based on a (configurable) CSI-RS with relatively lowdensity so as to effectively use DL resources. Accordingly, onlytransmission modes (TMs) (e.g., TM 8, 9, or 10), in particular, based ona DM-RS among legacy defined DL TMs may be managed (i.e., set as a DL TMof a UE allocated the NCT) and DL data scheduling through the NCT may beconsidered.

Synchronization/tracking and various measurements may be required forthe NCT. To this end, primary synchronization signal (PSS)/secondarysynchronization signal (SSS) with the same or different configurationfrom the legacy LTE Release-8/9/10 may be set to be transmitted. Forexample, compared to in LCT, in the NCT, a relative order betweensynchronization signals (SSs), an SS transmission OFDM symbol position,and so on may be changed, and/or a CRS may be set to be partiallytransmitted on the time domain (e.g., k (e.g. k=1) subframe periodshaving specific periods) and the frequency domain (e.g., domaincorresponding specific n (e.g. n=6) RB (pairs)). In addition, in theNCT, the CRS may be set to be transmitted through one specific antennaport. A CRS that is transmitted in this form mainly forsynchronization/tracking and so on may not be used as an RS fordemodulation of a control channel and DL data.

FIG. 11 illustrates exemplary subframe structures of LCT and NCT.Referring to FIG. 11, the LCT may use an L-PDCCH and the NCT may use aUE-specific RS (e.g., DM-RS)-based E-PDCCH. In the NCT, the E-PDCCH maybe positioned from an initial OFDM symbol of a subframe unlike in FIG.12 to be described below. The frequency domain of the LCT and thefrequency domain of the NCT may at least partially overlap (Case 1) ormay not overlap (Case 2). Case 1 may be a case in which the LCT and theNCT are managed by different eNBs and Case 2 may be a case in which theLCT and the NCT are managed by different eNBs or the same eNB.

An advanced system including 3GPP LTE Release-11 has introducedUE-specific DMRS-based enhanced PDCCH or EPDCCH (E-PDCCH) for enhancingperformance and efficiency of a control channel, and so on. The EPDCCHmay be configured to be transmitted across physical resource block (PRB)pairs (including a legacy PDSCH region) on the time axis. In moredetail, a search space (SS) for EPDCCH detection may include one or more(e.g., 2) EPDCCH sets, each EPDCCH set may occupy a plurality of (e.g.,2, 4, or 8) PRB pairs, and an enhanced CCE or eCCE (ECCE) included ineach EPDCCH set may be mapped to be localized or distributed (accordingto whether one ECCE is spread in a plurality of PRB pairs). In addition,when EPDCCH-based scheduling is set, a subframe for performing EPDCCHtransmission/detection may be determined. In addition, the EPDCCH mayconstitute only a UE-specific search space (USS). Accordingly, the UEmay attempt to detect (DCI) only on a PDCCH common search space (CSS)and an EPDCCH USS in a subframe in which EPDCCH transmission/detectionis set and attempt to detect DCI only on a PDCCH CSS and a PDCCH USS ina subframe in which EPDCCH transmission/detection is not set. In thisspecification, the subframe in which EPDCCH transmission/detection isset may be referred to as an EPDCCH subframe and the subframe in whichEPDCCH transmission/detection is not set may be referred to as anon-EPDCCH subframe.

FIG. 12 illustrates an example in which a DL physical channel isallocated to a subframe.

Referring to FIG. 12, a PDCCH (for convenience, legacy PDCCH, LPDCCH, orL-PDCCH) according to legacy LTE Release-8/9/10 may be allocated to acontrol region of a subframe. In the drawing, a LPDCCH region may referto a region to which the legacy PDCCH can be allocated. According to thecontext, the LPDCCH region may refer to a control region or a controlchannel resource region (i.e., CCE resources) or a PDCCH search space,to which a PDCCH can be actually allocated in the control region. AnEPDCCH may be further allocated in a data region (e.g., a resourceregion for a PDSCH). As illustrated in the drawing, control channelresources may be additionally ensured through an EPDCCH so as toalleviate scheduling restriction due to limited control channelresources of the LPDCCH region.

In the case of an EPDCCH, a USS may be configured with K E-PDCCH set(s)(for each CC/cell) from one UE point of view. For example, K may begreater than or equal to 1 and may be equal to or less than a specificupper limit (e.g., 2). In addition, each EPDCCH set may be configuredwith specific N PRBs (which belong to a PDSCH region). N andresource/index of a PRB included in the N PRBs may be independently(i.e., set-specifically) allocated. Accordingly, a resource number andindex of ECCE included in each EPDCCH set may also be set-specificallyset (while being UE-specifically), and in the case of a PUCCHresource/index linked with each corresponding ECCE resource/index, anindependent starting PUCCH resource/index may be configured for eachEPDCCH set so as to have (UE-specifically) and set-specificallyallocated structure. Here, the ECCE resource/index may refer to a basiccontrol channel unit of an EPDCCH including a plurality of REs (whilebelong to a PRB in a PDSCH region) and may have different configurationsaccording to a transmission type of an EPDCCH. For example, an ECCE forlocalized transmission may be configured using an RE belonging to thesame PRB pair, whereas an ECCE for distributed transmission may beconfigured by extracting an RE from a plurality of PRB pairs. In thecase of a localized ECCE, in order to perform beamforming optimized foreach different user using each ECCE, an independent antenna port (AP)for each ECCE resource/index may be associated, and in the case of adistributed ECCE, sets of the same AP may be repeatedly associated indifferent ECCEs such that a plurality of users commonly uses a series ofAPs.

A TDD-based legacy LTE Release-8/9/10 system requires a transceivingtiming gap containing a transceiving switching gap for transceivingoperation switching to a UL subframe (SF) from a DL SF. To this end, aspecial SF may be managed between the corresponding DL SF and UL SF. Forexample, various special SF configurations may be supported as shown inTable 2 above according to a situation such as a radio condition and aUE location. In addition, lengths of a DL period (e.g., DwPTS) and a ULperiod (e.g., UpPTS) that can be configured according to a CPcombination (normal or extended) used for DL/UL in a special subframe.Here, a special SF configuration or special SF in which the DL period(e.g., DwPTS) includes only three OFDM symbols may be referred to as a“shortest S” for convenience. For example, as shown in Table 2 above, inthe case of a normal CP, special SF configurations #0 and #5 in DL maybe the shortest S, and in the case of extended CP, special SFconfigurations #0 and #4 in DL may be the shortest S.

FIG. 13 illustrates an example of an OFDM symbol number of a DL period(e.g., DwPTS), a guard period (e.g., GP), and a UL period (e.g., UpPTS)according to the special SF configuration of Table 2 above. Forconvenience, FIG. 13 illustrates an example in which a normal CP is used(i.e., 14 OFDM symbols per SF). Referring to FIG. 13, the number of OFDMsymbols to be used in a DL period (e.g., DwPTS) may be changed accordingto a special SF configuration. For example, in the case of special SFconfigurations #0 and #5, initial three OFDM symbols in a first slot maybe used as a DL period (e.g., DwPTS). On the other hand, in the case ofspecial SF configurations #1, #2, #3, #4, #6, #7, and #8, all OFDMsymbols of a first slot may be used as a DL period (e.g., DwPTS).

As described above, when the shortest S is configured, a demodulationreference signal (DMRS) cannot be transmitted due to a short DL period(e.g., DwPTS). Accordingly, when the shortest S is configured, a DLsignal (e.g., a control channel signal and a data channel signal) may bedemodulated based on a CRS.

In this case, when the NCT is managed in a TDD manner (for at least DL),a CRS may be set so as not to be transmitted through a DL period (e.g.,DwPTS) in the shortest S or even if the CRS may be set so as to betransmitted in the DL period (e.g., DwPTS) in the shortest S, the CRSmay be used only for synchronization/tracking and may not be used fordemodulation of control channel and DL data. In this case, when a DMRSis not defined in the NCT with respect to a DL period (e.g., DwPTS) inthe shortest S like in the legacy LTE Release-8/9/10, three OFDM symbolsin the corresponding DL period (e.g., DwPTS) cannot be used both for DLdata transmission as well as for (legacy LPDCCH-based) control channeltransmission. Accordingly, DL resources may be wasted compared with anexisting legacy carrier providing backward compatibility.

Embodiment 1

Accordingly, the following options may be considered with respect tomethods for using and configuring a shortest S for TDD-based NCTmanagement. In detail, methods of options 0 to 5 may be considered. Atleast two of options except for options 0 and 1 may be combined andapplied. For example, it may be possible to apply only options 2 and 3to a DL period (e.g., DwPTS) in the shortest S of the TDD NCT. Here, aPDCCH to be described later may include both a LPDCCH and an EPDCCH.

Option 0: Special SF Configuration Except for Shortest S

With respect to the TDD NCT, a shortest S-based special SF configuration(e.g., #0 and #5 in the case of normal CP in DL and #0 and #4 in thecase of extended CP in DL) may not be supported. Option 0 may be usefulin that the NCT is mainly a secondary carrier that is additionallyaggregated to a legacy carrier and coverage can be deployed at anappropriate level (so as not to be excessively large) in order toenhance resource/power use efficiency.

Option 1: No PDCCH and No DL Data in Shortest S

Both PDCCH transmission and DL data transmission may not be allowed withrespect to a DL period (e.g., DwPTS) in the shortest S configured in theTDD NCT. Accordingly, a UE may omit a series of operations associatedwith blind detection for PDCCH detection and demodulation for DL datareception with respect to the corresponding period. As another method,in the case of the shortest S only, an operation (e.g., UL granttransmission) configured to be performed through the DL period (e.g.,DwPTS) in the corresponding shortest S may be performed instead inanother specific carrier that is not the corresponding NCT (e.g.,through a cross-CC scheduling method). In this case, the specificcarrier may be, for example, a primary cell Pcell.

Option 2: E-PDCCH Based UL Grant in Shortest S

With respect to a DL period (e.g., DwPTS) in the shortest S configuredin the TDD NCT, only EPDCCH-based UL grant may be allowed. In this case,a separate demodulation RS (having a similar configuration to a DMRS forDL data reception) may be transmitted for corresponding UL grant EPDCCHdetection. In this case, the separate demodulation RS may be referred toas an enhanced DMRS (E-DMRS).

Option 3: Cross-CC Scheduled DL Data in Shortest S

With respect to a DL period (e.g., DwPTS) in the shortest S configuredin the TDD NCT, only cross-CC scheduled DL data transmission from DLgrant PDCCH transmitted through another carrier may be allowed. In thiscase, for DL data reception, the DMRS may be transmitted. For example,when the NCT is not configured in a cross-CC scheduling mode, cross-CCscheduling from another (predetermined) carrier may be restrictivelyallowed with respect to only a corresponding shortest S.

Option 4: Cross-SF Scheduled DL Data in Shortest S

Only cross-SF scheduled DL data transmission from a DL grant PDCCHtransmitted through a previous DL SF (i.e., a D subframe) of acorresponding S SF may be allowed with respect to a DL period (e.g.,DwPTS) in the shortest S configured in the TDD NCT. To this end, thefollowing three methods may be considered.

-   -   DL grant/DL data for each D subframe and S subframe: different        DL data may be transmitted in D and S subframes, and DL grant        PDCCH for each DL data may also be separately transmitted        through the corresponding D subframe. In this case, an indicator        for identifying an SF (D or S) for transmitting DL data may be        signaled in the corresponding DL grant PDCCH. In this case, a        DMRS for reception of DL data (which is transmitted through the        S subframe) may be transmitted through a DL period (e.g., DwPTS)        in the shortest S.    -   One DL grant over D and S subframes/DL data for each D and S        subframe: Different DL data may be transmitted in each of D and        S subframes and one DL grant PDCCH may be transmitted through        the corresponding subframe D with respect to the two        corresponding SFs. In this case, an indicator for identifying a        SF (both D and S subframes, only D, or only S) for transmitting        DL data may be signaled in the corresponding DL grant PDCCH. In        this case, a DMRS for reception of DL data (transmitted through        the S subframe) may be transmitted through a DL period (e.g.,        DwPTS) in the shortest S. When DL data is transmitted in both D        and S subframes, a channel estimation result based on the DMRS        transmitted through the D subframe may be reused for reception        of DL data transmitted in a (immediately next) S subframe as        well as reception of DL data transmitted in the D subframe. In        this case, only DL data may be received without DMRS        transmission in a DL period (e.g., DwPTS) in the shortest S.    -   One DL grant/DL data over D and S subframes: One DL data may be        transmitted over the D and S subframes and one DL grant PDCCH        for the DL data may be transmitted through the corresponding D        subframe. For example, DL data may be set to be always        transmitted over both the D and S subframes or set to be        selectively transmitted in both the D and S subframes, only in        the D subframe, or only in the S subframe. For example, when DL        data is set to be selectively transmitted in the D and/or S        subframes, a DMRS may be transmitted through a DL period (e.g.,        DwPTS) in the shortest S, and an indicator for identifying a        region (both D and S subframes, only D, or only S) for        transmitting DL data may be signaled in a corresponding DL grant        PDCCH. When DL data is transmitted over both the D and S        subframes, channel estimation result based on the DMRS        transmitted through the D subframe may be reuse for reception of        a part of DL data transmitted in a (immediately next) S subframe        as well as for reception of a part of DL data transmitted in the        D subframe. Accordingly, in this case, only DL data may be        received without DMRS transmission in a DL period (e.g., DwPTS)        in the shortest S.

Option 5: E-PDCCH Based DL Grant and Corresponding DL Data in Shortest S

With respect to a DL period (e.g., DwPTS) in a shortest S configured inthe TDD NCT, only EPDCCH configuration-based DL grant transmission andDL data transmission corresponding thereto may be allowed. In this case,an E-DMRS and DMRS for detection/reception of the corresponding DL grantEPDCCH and DL data corresponding thereto may be transmitted.

In some options of the aforementioned options (Options 0 to 5), when DLdata is transmitted in a DL period (e.g., DwPTS) in the shortest S, amethod for determining a transport block size needs to be changed. Acurrent 3GPP LTE Rel-8/9/10 system may determine a transport block sizeusing a table represented with a combination of the number of resourceblocks (RBs) determined in DL assignment information (or DL grant) and amodulation and coding scheme (MCS). Accordingly, when an eNB determinesthe number of RBs and a MCS, the number of transmitted bits may beautomatically determined. The transport block size is affected by thenumber of OFDM symbols available for corresponding DL data. In thisregard, like in the aforementioned options, when DL data is transmittedusing only a very small number of OFDM symbols in the shortest S, a newtransport block size table appropriate for this may be required. Indetail, when separate DL data (e.g., codeword) is transmitted throughonly a DL period (e.g., DwPTS) of the shortest S, a transport block sizetable calculated under the assumption that, for example, three OFDMsymbols are used may be used. When one DL data (e.g., codeword) istransmitted over a legacy DL SF and shortest S, a transport block sizetable calculated under the assumption that OFDM symbols corresponding tothe sum of OFDM symbol number used in the DL SF and the shortest S maybe used.

As another for determining a transport block size, an existing transportblock size table defined for a general DL subframe (SF) of a legacycarrier may be referred to without changes, and a transport block sizemay be determined by considering a value obtained by multiplying RBnumber (N′_(PRB)) that is actually allocated through DL grant by aspecific weighting factor as a RB number N_(PRB) defined in acorresponding transport block size table. Here, the weighting factor maybe determined as a ratio of the number of OFDM symbols available in themethod (e.g., a region obtained by summing the normal DL SF and theshortest S) compared with the number of OFDM symbols available in anormal DL SF. For example, when separate DL data (e.g., codeword) istransmitted through only a DL period (e.g., DwPTS) of the shortest S,N_(PRB)=max{flooring(N′_(PRB)×α),1} may be used (0<α<1). When one DLdata (e.g., codeword) is transmitted over the DL SF and the shortest S,N_(PRB)=max{flooring(N′_(PRB)×β),1} may be used (1<β<2). In this case,for example, α=0.25 and β=1.25.

In the case of a control channel resource unit (e.g., E-CCE)constituting an E-PDCCH (candidate), four or three E-CCEs may be mappedper PRB in consideration of RS overhead, etc. in a normal DL SF(including 14 (normal CP) or 12 (extended CP) OFDM symbols).Accordingly, in the case of an option in which E-PDCCH transmission isallowed among the aforementioned options, one E-CCE may be mapped byconsidering that only three OFDM symbols in a DL period (e.g., DwPTS) inthe shortest S are available.

In the case of a DM-RS (for a normal CP) in legacy Release-10, 8 antennaports may be divided into 2 code division multiplexing (CDM) groups, andan RS for 4 antenna ports included in each CDM group may beCDM-multiplexed on an RE group including 4 REs using a length-4 spreadcode (e.g., an orthogonal code). In this case, each CDM group may bemapped to a different RE group, and 4 REs constituting one RE group maybelong to different OFDM symbols. However, in the case of a DL period(e.g., DwPTS) in the shortest S, only 3 OFDM symbols are available, andthus a DM-RS configuration of a legacy Release-10 cannot be reusedwithout changes. Accordingly, in the case of an option in which DM-RSand E-DM-RS transmission is allowed among the aforementioned options, 4or 2 antenna ports may be divided into 2 or 1 CDM groups, respectively,and an RS for 2 antenna ports included in each CDM group may beCDM-multiplexed in an RE group including 2 REs using a length-2 spreadcode. In this case, each CDM group may be mapped to a different REgroup, and 2 REs constituting one RE group may belong to different OFDMsymbols. Alternatively, in the case of a NCT shortest S, an RS for 2 or1 antenna ports may be mapped to a RE group including 2 different REsfor each antenna port without CDM. In this case, an RS for each antennaport may be mapped to a different RE group and 2 REs constituting one REgroup may belong to different OFDM symbols.

FIG. 14 illustrates an example of a DM-RS configuration according to thepresent invention. In this example, assuming that 4, 2, and 1 antennaports in the above proposal are DM-RS antenna ports {7, 8, 9, 10}, {7,8}, and {7} in Rel-10, respectively, for convenience of description, theDM-RS configuration shown in FIG. 14 may be considered for a DL period(e.g., DwPTS) in the shortest S of a TDD NCT. In this case, for example,a sequence used for CDM between DM-RS antenna port {7, 8} may be usedwithout changes as a sequence for applying length-2 CDM in the case ofextended CP in Rel-10. In this case, for example, [+1, +1] and [−1, +1]may be reused as the length-2 sequence.

In addition, DL data (and/or E-PDCCH) transmission rank may be limitedwith respect to the shortest S of the TDD NCT so as to map only oneantenna port (e.g., DM-RS antenna port 7 of Rel-10) to a RE groupincluding 2 REs (which belong to different OFDM symbols) without CDM/FDMand to transmit the antenna port. For example, a single antennaport-based DM-RS (and/or E-DM-RS) may be transmitted using only a REcorresponding to one antenna port (e.g., 7 or 9) in FIG. 14, a singleantenna port-based DM-RS (and/or E-DM-RS) may be transmitted using allREs corresponding to all antenna ports (e.g., 7, 8, 9, and 10) in FIG.14, or a single antenna port-based DM-RS (and/or E-DM-RS) may betransmitted using an RE group including one RE belong to each CDM group.In this case, DL data is received using only a single DM-RS antennaport, and thus a DCI format used for scheduling of DL data transmittedthrough the shortest S of the TDD NCT may be limited to only DCI format1A (as TM-common DCI format). For example, TM-dedicated DCI format(e.g., DCI format 2C) transmission may not be allowed. Accordingly, a UEmay perform only a blind decoding operation for DCI format 1A on theshortest S of the TDD NCT (scheduling of DL data transmitted through thecorresponding SF).

Embodiment 2

Assuming that only antenna port #0 is used in legacy 3GPP Rel-10, a CRSand a PSS may be transmitted through the first (or initial) OFDM symboland the third OFDM symbol in a DL period (e.g., DwPTS) in the shortestS, respectively. Here, when a CRS pattern for antenna port #0 of legacy3GPP Rel-10 is reused, a problem may occur when the proposed options areapplied according to whether a CRS and/or a PSS (and/or a SSS) istransmitted in a DL period (e.g., DwPTS) in the NCT shortest S. Asolution for this will now be described as follows. Basically, it isassumed that a CRS, a PSS, and an SSS are transmitted through differentOFDM symbols.

Case 1: No CRS, No PSS/SSS in Shortest S

All CRS/PSS/SSS may be set not to be transmitted in a DL period (e.g.,DwPTS) in a NCT shortest S. In this case, all the proposed options canbe applied. In this case, a DM-RS (e.g., E-DM-RS) may be transmittedusing a RE of two adjacent OFDM symbols (e.g., the first and second OFDMsymbols or the second and third OFDM symbols) (refer to FIG. 14).

Case 2: No CRS, PSS or SSS in Shortest S

Only a PSS or an SSS may be set to be transmitted and only a PSS or aSSS may be set not to be transmitted in a DL period (e.g., DwPTS) in theNCT shortest S. In this case, all the proposed options can be applied. ADM-RS (e.g., E-DM-RS) in the NCT shortest S may be transmitted using anRE of the remaining two OFDM symbols (e.g., the first and second OFDMsymbols) except for an OFDM symbol (e.g., the third OFDM symbol) inwhich PSS/SSS is transmitted.

Case 3: No CRS, PSS and SSS in Shortest S

All PSS/SSS may be set to be transmitted and a CRS may be set not to betransmitted in a DL period (e.g., DwPTS) in the NCT shortest S. In thiscase, Option 1 or Option 4 (some methods that do not use DM-RStransmission) can be applied in a RB region in which PSS/SSS istransmitted in the NCT shortest S. On the other hand, an optionavailable in Case 1 and a DM-RS (e.g., E-DM-RS) configuration may beapplied in other RB regions in the NCT shortest S.

Case 4: CRS, No PSS/SSS in Shortest S

Only a CRS may be set to be transmitted and all PSS/SSS may be set notto be transmitted in a DL period (e.g., DwPTS) in the NCT shortest S. Inthis case, all the proposed options can be applied. A DM-RS (e.g.,E-DM-RS) in the NCT shortest S may be transmitted using an RE of theremaining two OFDM symbols (e.g., the second and third OFDM symbols)except for an OFDM symbol (e.g., the first or initial OFDM symbol) inwhich a CRS is transmitted.

Case 5: CRS, PSS and/or SSS in Shortest S

A PSS and/or an SSS as well as a CRS may be set to be transmitted in aDL period (e.g., DwPTS) in the NCT shortest S. In this case, Option 1 orOption 4 (some methods that do not use DM-RS transmission) can beapplied in an RB region in which PSS/SSS is transmitted in the NCTshortest S. On the other hand, an option available in Case 4 and a DM-RS(e.g., E-DM-RS) configuration may be applied in other RB regions in theNCT shortest S.

An E-CCE mapping method for E-PDCCH transmission may be detailed basedon the this, one E-CCE may be set/allocated per one or two PRBs or anE-CCE may not be set/allocated to a specific PRB according to the numberof REs that are occupied by an RS (e.g., E-DM-RS) and/or SS (e.g., PSSand/or SSS) in a DL period (e.g., DwPTS) of a (shortest) special SF. Forexample, an E-CCE may not be allocated in a PRB in a region in which anSS is transmitted and one or two E-CCEs may be allocated per one or twoPRBs in a region in which an SS is not transmitted, or one E-CCE may beallocated per two PRBs in a region in which a SS is transmitted and oneE-CCE may be allocated per one PRB in a region in which a SS is nottransmitted. For example, in the case of a region in which an RS for aplurality of antenna ports (without SS transmission) is transmitted inthe form of FDM, one E-CCE per one PRB may be allocated, and in the caseof a region in which an RS for a single or a plurality of antenna ports(without SS transmission) is transmitted without FDM (and/or withoutDCM) (e.g., an RS is transmitted using all REs corresponding to theantenna ports 7, 8, 9, and 10 in FIG. 14), one E-CCE may be allocatedper two PRBs. As another example, one E-CCE may be set/allocated per PRBirrespective of RS and SS overhead in a DL period (e.g., DwPTS) of theshortest S and blind decoding for E-PDCCH detection may be performedonly on two or more E-CCE aggregation levels, or one E-CCE may beset/allocated per two PRBs irrespective of RS and SS overhead and blinddecoding for E-PDCCH may be performed on all E-CCE aggregation levels(including 1). For example, separately from a search space (i.e., anE-PDCCH PRB set) for E-PDCCH detection in a normal DL SF, a search space(i.e., E-PDCCH PRB set) for E-PDCCH detection in a (shortest) special SFand a number of times of blind decoding for each E-CCE aggregation levelaccording to the search space may be independently set/allocated.

The application of the aforementioned methods (Options 1 to 5 accordingto Cases 1 to 5 and combinations thereof, and the proposedconfigurations of DM-RS/E-DM-RS) may not be limited only to a TDD NCT inwhich the shortest S is set. For example, the aforementioned methods canbe collectively applied to a case in which all arbitrary special SFs(including a shortest S) are set in a TDD NCT or a special SF in which aDL period (e.g., DwPTS) generally includes N or less OFDM symbols is setin a TDD NCT. Alternatively, a method among the aforementioned methodsmay be set cell-specifically or UE-specifically. Here, N may be apositive integer and may be, for example, 7 (normal CP case) or 6(extended CP case) which corresponds to the number of OFDM symbols inone slot in a normal DL SF. Alternatively, N=3 irrespective of CP.

The NCT may also be seriously affective by various control channels/RSsignals transmitted through an L-PDCCH region on a legacy carrier. Toprevent interference, an E-PDCCH start symbol position (e.g.,E-PDCCH_startSym) for the NCT and/or a DL data start symbol position(e.g., DL-data_startSym) may be set. Assuming that an OFDM symbol indexis started from #0 in an SF, E-PDCCH_startSym and DL-data_startSymvalues may be 0 to 3 (or 0 to 4). In this case, in consideration of theE-PDCCH_startSym and DL-data_startSym values, the proposed method may beadaptively applied to an arbitrary special SF set in the NCT or aspecial SF in which a DL period (e.g., DwPTS) includes N or less OFDMsymbols.

In detail, different methods may be applied to a case in whichE-PDCCH_startSym and DL-data_startSym have a value equal to or more thanK and a case in which E-PDCCH_startSym and DL-data_startSym have a valueless than K. K=2 (or K=3) may be satisfied. In detail, when theE-PDCCH_startSym and DL-data_startSym values are equal to or more thanK, Option 1 (or some methods that do not use DM-RS transmission inOption 4) may be applied, and when the E-PDCCH_startSym andDL-data_startSym values are less than K, all options may be applied. Inaddition, from a point of view of a size of an RE group in which DM-RS(e.g., E-DM-RS) is mapped/transmitted, when the E-PDCCH_startSym andDL-data_startSym values are equal to or more than K, Option 1 or a 2-REconfiguration-based DM-RS transmission method (similar to FIG. 14) maybe applied. That is, the DM-RS may be mapped to a RE group including 2REs belonging to different OFDM symbols. On the other hand, when theE-PDCCH_startSym and DL-data_startSym values are less than K, a 4-REconfiguration-based DM-RS transmission method similar to legacy 3GPPRel-10 may be applied. That is, the DM-RS may be mapped to an RE groupincluding 4 REs belonging to different OFDM symbols.

For example, when the E-PDCCH_startSym and/or DL-data_startSym valuesare given by a value equal to or more than 2 with respect to a TDD NCTin which a shortest S including only 3 OFDM symbols in a DL period(e.g., DwPTS) is set as described above, the number of actuallyavailable OFDM symbols may be limited to 1 or less. Accordingly, anoption (e.g., Options 2, 3, and 5 and some methods that use DM-RStransmission in Option 4) in which E-PDCCH and/or DL transmissionthrough only the shortest S is allowed among the aforementioned optionsmay be excluded and Option 1 (or some methods that do not use DM-RStransmission in Option 4) may be applied. In the same condition as theaforementioned condition, on the other hand, when theE-PDCCH_(—)startSym and/or DL-data_startSym values are given by a valueless than 2, two or more actually available OFDM symbols are ensured,and thus all the aforementioned options can be applied.

As another example, assuming a TDD NCT in which a special SF including 6OFDM symbols in a DL period (e.g., DwPTS) is set, when E-PDCCH_startSymand/or DL-data_startSym values are given by a value equal to or morethan 3, the number of actually available OFDM symbols is limited to 3 orless, and thus an Option 1 or 2-RE configuration-based DM-RS/E-DM-RStransmission method (similar to FIG. 14) may be applied. In the samecondition as the aforementioned condition, on the other hand, when theE-PDCCH_startSym and/or DL-data_startSym values are given by a valueless than 3, 4 or more actually available OFDM symbols can be ensured,and thus a legacy 4-RE configuration-based DM-RS/E-DM-RS transmissionmethod may be applied.

In the method for applying different methods according to theE-PDCCH_startSym and DL-data_startSym values, the “number of actuallyavailable OFDM symbols” may be calculated in consideration of only anOFDM symbol (e.g., an OFDM symbol in which PSS/SSS/CRS, etc. are nottransmitted) available for DM-RS/E-DM-RS. K as a reference for applyingdifferent methods may be differently determined in the proposed methodaccording to the calculated “number of actually available OFDM symbols”.

As another example, in the case of TDD NCT, E-PDCCH_startSym and/orDL-data_startSym values to be applied to a shortest S (or all arbitraryspecial SFs or a special SF including specific N or less OFDM symbols ina DL period (e.g., DwPTS)) may be independently set (separately from ina normal DL SF) or fixed E-PDCCH_startSym and/or DL-data_startSym valuesthat are always predetermined/predefined (e.g., the first OFDM symbolindex #“0”) may be applied to a corresponding (shortest) special SF.

All methods and principles according to the present invention may beapplied in the same/similar way irrespective of division of FDD/TDDand/or a carrier type (e.g., NCT or LCT). For example, even if a methodaccording to the present invention applies a differentform/configuration from a general signal/channelconfiguration/transmission method in the legacy LCT, configurability forapplication of the method according to the present invention may beprovided to an advanced UE (e.g., a UE supporting NCT) on the legacy LCTas a target. For convenience of description, legacy DCI for schedulingone fixed SF may be defined as single-SF DCI and DCI for performingsimultaneous scheduling of a plurality of SFs or selective scheduling ofone or more SFs may be defined as multi-SF DCI or cross-SF DCI.

It may be possible to extend and generalize the aforementioned method toapply different E-PDCCH_startSym and/or DL-data_startSym valuesaccording to a situation/condition. In detail, the E-PDCCH_startSymand/or DL-data_startSym values to be applied to each SF or each SF setmay be independently set/defined. For example, assuming 2 SF set #1 and#2, the E-PDCCH_startSym and/or DL-data_startSym values may be differentapplied such that the E-PDCCH_startSym and/or DL-data_startSym values inSF set #1 are OFDM symbol index #0 and the E-PDCCH_startSym and/orDL-data_startSym values in SF set #2 are OFDM symbol index #3. Thismethod may be effective to enhance throughput in consideration ofUE/control load and/or almost blank subframe (ABS) configuration-based)time-domain inter-cell interference coordination (ICIC), etc., and/orE-PDCCH_startSym and/or DL-data_startSym values to be applied to each RBor each RB group (or each EPDCCH set) may be independently set/defined.This setting may be performed via higher layer signaling (e.g., RRCsignaling) or DL grant (that schedules corresponding DL data in the caseof DL data). For example, independent E-PDCCH_startSym and/orDL-data_startSym values may be set/defined and applied with respect tosingle-SF DCI and DL data corresponding thereto, and multi-SF/cross-SFDCI and DL data corresponding thereto.

In addition, when E-PDCCH_startSym and/or DL-data_startSym are referredto as E-PDCCH/DL-data_startSym for convenience, whether rate-matching isapplied to a specific control channel during transmission/reception ofE-PDCCH/DL-data according to each EPDCCH set, eachE-PDCCH/DL-data_startSym value, or a E-PDCCH/DL-data_startSym value(e.g., when E-PDCCH/DL-data_startSym is set/defined to the same value asa specific value (e.g., OFDM symbol index #0) or a value less/equal toor more than the specific value) may be (independently) set/defined. Inthe present invention, rate-matching may include a puncturing operation,and/or whether rate-matching is applied to a specific control channelduring transmission/reception of E-PDCCH/DL-data in each UE or each SF(set) may be (independently) set/defined. In this case, for example, thecontrol channel to which rate-matching can be applied may beset/determined using PCFICH and/or (an entire portion or partialdetermined portion of) PHICH and/or (an entire portion or partialdetermined portion of) CSS, and it may be possible to set/define whetherrate-matching is applied to each of them. In addition, for example, thisconfiguration may be performed via higher layer signaling (e.g., RRCsignaling) or DL grant (for scheduling corresponding DL data in the caseof DL data). For example, whether rate-matching may be independentlyapplied to single-SF DCI and DL data corresponding thereto, andmulti-SF/cross-SF DCI and DL data corresponding thereto may be(independently) set/defined and applied.

In addition, an EPDCCH set configured in each SF (set) and relatedinformation may also be independently set for each SF (set) inconsideration of application of E-PDCCH/DL-data_startSym for each SF(set) and/or application of control channel rate-matching for each SF(set). For example, the related information may includeE-PDCCH/DL-data_startSym set/corresponding to the number of EPDCCH set(e.g., 1 or 2), a size of each set (e.g., 2, 4, or 8 PRBs), and eachset, an EPDCCH transmission type (e.g., localized or distributed ECCE)and DMRS scrambling sequence/parameter set for each set, EREG/ECCEconfiguration information and ECCE aggregation level/blind decodinginformation allocated for each set, implicit PUCCH (e.g., PUCCH format1a/1b) resource start offset and explicit PUCCH (e.g., PUCCH format1a/1b/3) resource set configuration set/corresponding to each set, andso on. In addition, for example, independent EPDCCH set and relatedinformation may be set and applied with respect to single-SF DCI andmulti-SF/cross-SF DCI (or SF (determined) as detection target ofmulti-SF/cross-SF DCI and the remaining SFs except therefor).

In the case of LCT, an EPDCCH candidate that (entirely or partially)overlap and is allocated with a PRB in which PSS/SSS and/or PBCH istransmitted may not be transmitted/received and/or a UE may not attemptto perform detecting/receiving operation on the corresponding EPDCCHcandidate. Accordingly, in consideration of this, in the case of LCT(for example, having a small system bandwidth (BW)), an SF in whichPSS/SSS and/or PBCH is transmitted may not be configured as an EPDCCHmonitoring SF (e.g., the corresponding SF is set to monitor L-PDCCH) soas to stably ensure/maintain control channel transmission change andscheduling freedom degree. On the other hand, in the case of NCT, whenthe aforementioned operation is also maintained while (CRS-based)L-PDCCH transmission is not allowed, it may be impossible to use a PRBin which PSS/SSS and/or PBCH is transmitted to transmit a controlchannel, and accordingly (in particular, in the case of an NCT that hasa small system BW and/or operating in a TDD manner) control channeltransmission change and scheduling freedom degree may be reduced toreduce throughput.

Accordingly, in the NCT, an EPDCCH candidate (which (entirely orpartially) overlaps and allocated with a PRB in which PSS/SSS and/orPBCH is transmitted) in a SF in which PSS/SSS and/or PBCH is transmittedmay be transmitted/received while rate-matching is applied to thecorresponding PSS/SSS and/or PBCH (unlike in the legacy LCT) (and/or theUE may attempt to perform detection/reception operations on thecorresponding EPDCCH candidate) and/or whether the corresponding EPDCCHcandidate is used, that is, whether the corresponding EPDCCH candidateis available or not (like in the legacy LCT) for control channeltransmission (based on rate-matching with respect to PSS/SSS and/orPBCH) may be set/defined. Whether the corresponding EPDCCH candidate isused may be independently set/defined with respect to each UE or each SF(set) (or for each EPDCCH set).

Embodiment 3

FIG. 15 illustrates collision of subframes in different cells. Referringto FIG. 15, a Pcell and a Scell may be determined as a special SF and aDL SF, respectively with respect to a UE that does not supportsimultaneous transceiving operation/capability (or operates in ahalf-duplex manner) (which is referred to as “half-duplex (HD) PcellS+Scell D (Pcell S+Scell D with HD)”). In this case, link directionsbetween two cells are different in a partial time period 1506 of thecorresponding subframe, and thus a UE may transmit and receive a signalto only one of the two cells. Likewise, when link directions aredifferent in a subframe of two aggregated cells in a UE that does notsupport simultaneous transceiving operation/capability (or operates in ahalf-duplex manner), it is said that cells or subframes collide. On theother hand, link directions of two cells correspond to each other in apartial time period 1502 of the corresponding subframe, and thus boththe two cells may receive a signal. Although two cells do not collide ina partial time period 1504 of the corresponding subframe, the period1504 is set as a guard period in the Pcell, and thus the UE may nottransmit and receive any signal.

In the case of half-duplex (HD) Pcell S+Scell D, the proposed methodsfor the (shortest) special SF according to the present invention may beapplied in the same/similar way to a DL SF of the corresponding Scell.In addition, the methods for the (shortest) special SF according to thepresent invention may also be applied in the same/similar way to aspecific SF (e.g., an SF set to perform detection/reception of PMCH) setas a MBSFN (irrespective of a frame structure type (e.g., FDD or TDD)).

In the case of NCT, in the example of “half-duplex Pcell S+Scell D”, aDL signal/channel may be received while only a symbol period (i.e., thesame symbol/configuration as the corresponding DwPTS) corresponding to aspecific DL period (e.g., DwPTS) is exceptionally assumed to bereceivable DL resources with respect to a DL SF of (NCT-based) Scell. Inthis case, the specific DL period may be 1) a DL period (e.g., DwPTS) ofa special SF set in a Pcell, 2) a DL period (e.g., DwPTS) of a specialSF set in a Scell, 3) a DL period (e.g., DwPTS) with a shorter lengthfrom a Pcell and a Scell, or 4) a DL period (e.g., DwPTS) with a smallernumber of symbols from a Pcell and a Scell, in the corresponding SF. Inthis case, the UE may receive, for example, a UL grant EPDCCH and a DMRSfor detection/reception thereof, and/or a PDSCH, a DL grant EPDCCH forscheduling the same, and a DMRS for detection/reception thereof in aspecific DL period. In this case, an EPDCCH search space configuration(e.g., EREG/ECCE mapping and configuration, an ECCE aggregation level,and a number of times of blind decoding) and/or DMRS transmission REmapping, etc. in the corresponding DL SF may be defined/configured touse EPDCCH/DMRS configuration/mapping applied to the specific DL period(which is not a normal DL SF) (i.e., corresponding DwPTS) (which isreferred to as Alt-1). Alternatively, a portion that uses EPDCCH/DMRSconfiguration/mapping applied to a normal DL SF without changes and ismapped/configured to resource (e.g., RE) outside the specific DL period(i.e., corresponding DwPTS) may not be used, rate-matched, or punctured(which is referred to as Alt-2). Alternatively, it may be possible toapply different methods (Alt-1 or Alt-2) to EREG/ECCE mapping andconfiguration, ECCE aggregation level, a number of times of blinddetection, and DMRS transmission RE mapping. Likewise, a method forapplying Alt-1 or Alt-2 to a specific DL period is referred to as“Method 1” for convenience.

In the case of NCT, any DL signal/channel reception may not be supportedin order to reduce complexity for embodying a UE in the example of“half-duplex Pcell S+Scell D”. This method is referred to as “Method 4”for convenience.

In the case of LCT, a UE may operate while assuming/considering thatonly PDCCH and/or PHICH transmission/reception is allowed,detection/reception of PDSCH/EPDCCH/PMCH/PRS is omitted/abandoned, orthere is no indication/scheduling with respect to PDSCH/EPDCCH/PMCH/PRSin a DL SF of a corresponding Scell in the example of “half-duplex PcellS+Scell D”. This method is referred to as “Method 2”.

In a CA situation in which SF timing between cells is not aligned (i.e.,based on staggered SF timing) or a CA situation of a UL-DL configurationto be further introduced in the future, there is the potential that aspecial SF in a specific cell and a UL SF of another specific cellcollide with each other at the same SF timing. In this situation, when aPcell is a special SF and a Scell is a UL SF, a UE that does not supportsimultaneous transceiving operation/capability (or operates in ahalf-duplex manner) may operate while assuming/considering that only SRStransmission is allowed in the corresponding Scell, for example,transmission of the remaining UL signal/channel (e.g.,PRACH/PUCCH/PUSCH) is omitted/abandoned or there is noindication/scheduling with respect to transmission of the remaining ULsignal/channel. On the other hand, when a Pcell is a UL SF and a Scellis a special SF, only UL transmission (e.g., SRS and/or PRACH) through aUL period (e.g., UpPTS period) is allowed in the corresponding Scell,for example, DL signal/channel transmission through a DL period (e.g.,DwPTS) is omitted/abandoned or there is no indication/scheduling withrespect to transmission of the DL signal/channel transmission. As such,the method applied when a UL SF and a special SF collide between a Pcelland a Scell is referred to as “Method 3”.

When a UL SF and a special SF collide between a Pcell and a Scell,transmission of any UL signal/channel may not be supported in order toreduce complexity for embody a UE. This method is referred to as “Method5” for convenience.

The collision handling method between a special SF and a DL/UL SF may beextensively applied to a CA situation between a TDD cell and a FDD cell.In detail, when the TDD cell and the FDD cell are carrier-aggregated,the collision handling method may also be extensively applied to thecase in which a special SF of the TDD cell and a DL/UL SF pair (or onDL/UL carriers constituting the pair) of the FDD cell are set at thesame SF timing. For example, when a special SF of the TDD Pcell and aDL/UL SF pair of the FDD Scell collide at the same SF timing, Method 1or 2 may be applied to a DL SF of the FDD Scell (according to acell/carrier type) and Method 3 may be applied to a UL SF of the FDDScell. As another example, when a special SF of the TDD Pcell and aDL/UL SF pair of the FDD Scell collide at the same SF timing, Method 1or 2 may be applied to a DL SF of the FDD Scell (according to acell/carrier type), whereas Method 3 may be applied to a UL SF of theFDD Scell while Method 5 is applied to a UL SF of the FDD Scell (i.e.,any UL signal/channel transmission is not supported) or Method 4 isapplied to a DL SF of the FDD Scell (i.e., any DL signal/channeltransmission is not supported). Alternatively, Methods 4 and 5 may beapplied to a DL SF and a UL SF of the FDD Scell, respectively in orderto reduce complexity for embodying a UE. In addition, the same/similaroperation/method as the aforementioned operation/method may also beapplied to an opposite combination of Pcell/Scell, i.e., to the case inwhich the FDD Pcell and the TDD Scell are carrier-aggregated.

Application of the operation/method (e.g., Methods 1 to 5) may not belimited only to a UE that does not support simultaneous transceivingoperation/capability (or operates in a half-duplex (HD) manner). Forexample, the same/similar operation/method as the above operation/method(Methods 1 to 5) may be applied to even a UE that supports simultaneoustransceiving operation/capability (or operates in a full-duplex (HD)manner) due to interference between DL/UL resources according to aninternal between carriers (e.g., TDD carrier, FDD DL carrier, and FDD ULcarrier) included in TDD and FDD cells. In this case, the same/similaroperation/method as the above operation/method (Methods 1 to 5) may beapplied irrespective of whether a UE has simultaneous transceivingoperation/capability and/or a frame configuration type of the Pcell andthe Scell (e.g., FDD or TDD). For example, when an interval between aTDD carrier and a FDD DL carrier is smaller than a specific value, if aTDD special SF and a FDD DL SF collide at the same SF timing, Method 1,2, or 4 may be applied to the corresponding FDD DL SF or Method 5 may beapplied to a corresponding TDD special SF. As another example, when aninterval between a TDD carrier and a FDD UL carrier is smaller than aspecific value, if a TDD special SF and a FDD UL SF collide at the sameSF timing, Method 3 or 5 may be applied to the corresponding FDD UL SFor Method 4 may be applied to the corresponding TDD special SF. Theabove method may be automatically set according to an interval betweenTDD/FDD carriers (i.e., when a corresponding interval satisfies aspecific condition) or may be set via higher layer signaling (accordingto an internal between TDD/FDD carriers or irrespective of thecorresponding interval).

Embodiment 4

As another approach, in the case of a TDD NCT, Alt-3), an entire orpartial UL period (e.g., UpPTS) in a shortest S may be omitted and a DLperiod (e.g., DwPTS) may be extended by as much as the omitted UL period(e.g., UpPTS), or on the other hand, Alt-4) an entire or partial DLperiod (e.g., DwPTS) in a shortest S may be omitted and a UL period(e.g., UpPTS) may be extended by as much as the omitted DL period (e.g.,DwPTS). In the case of Alt-3, the aforementioned Options 1 to 5 and theproposed DM-RS/E-DM-RS configuration may be applied with modification orwithout changes to the extended DL period (e.g., DwPTS) according to thebasic principles proposed in the aforementioned Cases 1 to 5, and in thecase of Alt-4, transmission of additional UL signal and data (e.g.,SRS/PRACH and/or PUSCH with a short length, etc.) may be set/allowedwith respect to the extended UpPTS period. More generally, in the caseof a TDD NCT, the aforementioned approach method (Alt-3 or Alt-4) may besimilarly introduced to all arbitrary special SFs (including theshortest S) or a special SF in which a DL period (e.g., DwPTS) includesspecific N or less OFDM symbols. That is, in the case of the TDD NCT, anentire or partial UL period (e.g., UpPTS) in a special SF may be omittedand a DL period (e.g., DwPTS) may be extended by as much as the omittedUL period (e.g., UpPTS), or on the other hand, an entire or partial DLperiod (e.g., DwPTS) in a special SF may be omitted and a UL period(e.g., UpPTS) may be extended by as much as the omitted DL period (e.g.,DwPTS).

Unlike a legacy special SF configuration including [DL period (e.g.,DwPTS)+guard period (e.g., Guard Period, GP)+UL period (e.g., UpPTS)], anew type of special SF including only [DL period (e.g., DwPTS)+guardperiod (e.g., GP)] or [guard period (e.g., GP)+UL period (e.g., UpPTS)]based on the aforementioned method or other methods may be consideredfor more flexible and effective use of DL/UL resources and datatransmission. For convenience of description, a special SF with [DLperiod (e.g., DwPTS)+guard period (e.g., GP)] configuration is referredto as “D-only-S” and a special SF with a [guard period (e.g., GP)+ULperiod (e.g., UpPTS)] configuration is referred to as “U-only-S”. Forconvenience of description, a legacy special SF with a [DL period (e.g.,DwPTS)+guard period (e.g., Guard Period, GP)+UL period (e.g., UpPTS)]configuration is referred to as “normal S”.

FIG. 16 illustrates an example of a special SF configuration. FIG. 16(B)illustrates D-only-S and FIG. 16(C) illustrates U-only-S. The length ofa DL period (e.g., DwPTS) in the D-only-S may be the same as ordifferent from the length of a DL period (e.g., DwPTS) of a normal S.For example, the length of a DL period (e.g., DwPTS) of the D-only-S maybe increased by a UL period (e.g., UpPTS) of a normal S based on thelength of a DL period (e.g., DwPTS) of the normal S. In addition, thelength of a UL period (e.g., UpPTS) in the U-only-S may be the same asor different from the length of a UL period (e.g., UpPTS) of the normalS. For example, the length of a UL period (e.g., UpPTS) of the U-only-Smay be increased by a DL period (e.g., DwPTS) of the normal S based onthe length of a UL period (e.g., UpPTS) of the normal S.

When a carrier aggregation (CA) situation including the special SF-basedcell is considered with respect to a UE that does not supportsimultaneous transceiving operation/capability (or operates in ahalf-duplex manner), it is required to determine/define a UE operationand signal processing method when different SFs between cells collide atthe same timing.

(Pcell, Scell)=(D-Only-S, DL SF)

In this case, Method 1 (when a corresponding Scell is a NCT) or Method 2(when the corresponding Scell is a LCT) may be applied to a DL SF of aScell. When Method 2 is applied, for example, only PDCCH and/or PHICHtransmission/reception may be allowed and detection/reception ofPDSCH/EPDCCH/PMCH/PRS may be omitted/abandoned (or a UE may operatewhile assuming/considering that there is no indication/scheduling withrespect to reception of corresponding DL signal/channel).

(Pcell, Scell)=(DL SF, D-Only-S)

In this case, a DL signal/channel receiving operation (which is the sameas in a non-CA situation) may be performed on an entire DL period (e.g.,DwPTS) of a Scell without separate restriction/limitation.

(Pcell, Scell)=(D-Only-S, UL SF)

In this case, Method 5 may be applied to a UL SF of a Scell. Forexample, UL signal/channel transmission in a UL SF of a Scell may beomitted/abandoned (or a UE may operate while assuming/considering thatthere is no indication/scheduling with respect to UL signal/channeltransmission).

(Pcell, Scell)=(UL SF, D-Only-S)

In this case, DL signal/channel reception may be omitted/abandoned withrespect to a DL period (e.g., DwPTS) of a Scell (or a UE may operatewhile assuming/considering that there is no indication/scheduling withrespect to DL signal/channel reception).

(Pcell, Scell)=(D-Only-S, Normal S)

In this case, UL signal/channel transmission may be omitted/abandonedwith respect to a UL period (e.g., UpPTS) of a Scell (or a UE mayoperate while assuming/considering that there is noindication/scheduling with respect to UL signal/channel transmission).

(Pcell, Scell)=(Normal S, D-Only-S)

In this case, Method 1 (when a corresponding Scell is a NCT) or Method 2(when the corresponding Scell is a LCT) may be applied to a DL period(e.g., DwPTS) of a Scell. When Method 2 is applied, only PDCCH and/orPHICH transmission/reception may be allowed and detection/reception ofPDSCH/EPDCCH/PMCH/PRS may be omitted/abandoned (or a UE may operatewhile assuming/considering that there is no indication/scheduling withrespect to reception of corresponding DL signal/channel).

(Pcell, Scell)=(U-Only-S, DL SF)

In this case, Method 4 may be applied to a DL SF of a Scell. Forexample, DL signal/channel reception may be omitted/abandoned withrespect to a DL SF of a Scell (or a UE may operate whileassuming/considering that there is no indication/scheduling with respectto DL signal/channel reception).

(Pcell, Scell)=(DL SF, U-Only-S)

In this case, UL signal/channel transmission in a UL period (e.g.,UpPTS) of a Scell may be omitted/abandoned (or a UE may operate whileassuming/considering that there is no indication/scheduling with respectto UL signal/channel transmission).

(Pcell, Scell)=(U-Only-S, UL SF)

In this case, only transmission of SRS (and/or PRACH) may be allowed ina UL SF of a Scell and transmission of PUSCH/PUCCH (and/or PRACH) may beomitted/abandoned (or a UE may operate while assuming/considering thatthere is no indication/scheduling with respect to transmission ofcorresponding UL signal/channel).

(Pcell, Scell)=(UL SF, U-Only-S)

In this case, a UL signal/channel transmission operation (which is thesame as in a non-CA situation) may be performed on an entire UL period(e.g., UpPTS) of a Scell without separate restriction/limitation.

(Pcell, Scell)=(U-Only-S, Normal S)

In this case, DL signal/channel reception may be omitted/abandoned withrespect to a DL period (e.g., DwPTS) of a Scell (or a UE may operatewhile assuming/considering that there is no indication/scheduling withrespect to DL signal/channel reception).

(Pcell, Scell)=(Normal S, U-Only-S)

In this case, only SRS (and/or PRACH) transmission may be allowed in aUL period of a Scell and transmission of PUSCH/PUCCH (and/or PRACH) maybe omitted/abandoned (or a UE may operate while assuming/consideringthat there is no indication/scheduling with respect to transmission ofcorresponding UL signal/channel).

(Pcell, Scell)=(D-Only-S, U-Only-S)

In this case, UL signal/channel transmission in a UL period (e.g.,UpPTS) of a Scell may be omitted/abandoned (or a UE may operate whileassuming/considering that there is no indication/scheduling with respectto UL signal/channel transmission).

(Pcell, Scell)=(U-Only-S, D-Only-S)

In this case, DL signal/channel reception may be omitted/abandoned (or aUE may operate while assuming/considering that there is noindication/scheduling with respect to DL signal/channel reception) withrespect to a DL period (e.g., DwPTS) of a Scell.

As described above, transmission of a PUSCH (with a short length) andscheduling therefor may also be allowed/supported through a UL period(e.g., UpPTS) in the case of a specific special SF (hereinafter,referred to as U-only-S) including U-only-S. UL grant reception timingfor scheduling PUSCH transmission and/or PHICH receiving timingcorresponding to the corresponding PUSCH transmission in the U-only-Smay be determined as a DL SF (e.g., SF #0 or #5) present 6 SFs beforefrom the corresponding U-only-S (e.g., SF #1 or #6) or a DL SF orspecial SF (e.g., SF #1 or #6) present before 5 SFs. For example, whenthe U-only-S is SF #1, the UL grant/PHICH receiving timing may bedetermined as SF #5 of an immediately previous radio frame (in the caseof 6 SFs before) or determined as SF #6 of an immediately previous radioframe (in the case of 5 SFs before). For example, when the U-only-S isSF #6, UL grant/PHICH receiving timing may be determined as SF #0 of thesame radio frame (in the case of 6 SFs before) or determined as SF #1 ofthe same radio frame (in the case of 5 SFs before).

In this case, the determined UL grant/PHICH receiving timing for theU-only-S may be determined to be the same as (predefined) UL grant/PHICHreceiving timing for a specific UL SF, and simultaneous/selectivescheduling may be performed on the U-only-S and/or a specific UL SFthrough a cross-SF scheduling method. In this case, in the case ofPHICH, 1) with respect to a UL SF, like an existing method, PHICHresource/index (referred to as PHICH-U) may be determined based on alowest PRB index and a DMRS cyclic shift, and a PHICH corresponding tothe U-only-S may be determined based on PHICH resource/index obtained byadding specific offset to PHICH-U. Alternatively, 2) with respect to aUL SF, like an existing method, non-adaptive retransmission based onPHICH (PHICH-U) reference is allowed, whereas non-adaptiveretransmission may not be allowed with respect to the U-only-S (based onACK signaling in an unconditional higher layer) and only adaptiveretransmission based on UL grant may be allowed without PHICH reference.Alternatively, 3) a PHICH corresponding to a UL SF and the U-only-S maybe determined as one legacy PHICH-U resource/index (i.e., ACK/NACKsignaled through corresponding PHICH-U may be interpreted/considered aslogical AND operation result between repletion responses in response toPUSCH transmission in the UL SF and the U-only-S).

In consideration of a CA situation in which SF timing between cells isnot aligned (i.e., based on staggered SF timing) or a CA situation of aUL-DL configuration to be further introduced in the future, independent(different) special SF configurations for respective special SF timing(e.g., SF #1 or SF #6) may be configured. When independent special SFconfigurations are configured, for example, the length and symbol numberof a DL period (e.g., DwPTS)/UL period (e.g., UpPTS), the length ofDL/UL CP, and so on may be independently (differently) configured. Forexample, in the case of SF #1, special SF configuration 0 may beconfigured, and in the case of SF #6, special SF configuration 1 may beconfigured.

In addition, it may be possible to configure independent (different)UL-DL configurations with respect to [SF #0 to SF #4] corresponding to afront portion of a radio frame and [SF #5 to SF #9] corresponding to arear portion of the radio frame. When the independent UL-DLconfigurations are configured, for example, an arrangement order of DLSF/UL SF/special SF may be independently (differently) may beconfigured. For example, UL-DL configuration 1 may be configured withrespect to [SF #0 to SF #4] and UL-DL configuration 2 may be configuredwith respect to [SF #5 to SF #9]. In this case, DL (DL grant/DLdata→HARQ-ACK) HARQ timing may be based on a specific UL-DLconfiguration in which entire D or S SF timing of the front and rearportions is determined as D or S, and UL (UL grant→UL data→PHICH) HARQtiming may be based on a specific UL-DL configuration in which entire USF timing of the front and rear portions is determined as U.

Embodiment 5

As another approach, in order to overcome issues in terms ofdata/control transmission/signaling with a small size/short length andtiming latency, etc. of HARQ (e.g., grant→data→feedback), a new SF type(referred to as “R” for convenience) configured in an period order of[UL period (e.g., UpPTS)+DL period (e.g., DwPTS)] and a new UL-DLconfiguration including the same may be considered. For example, R maybe arranged immediately after U or S and cannot be arranged immediatelyafter D or R. In addition, D or R may be arranged immediately after R,and U or R cannot be arranged immediately after R.

For example, U positioned between U and D or S and D in the legacy UL-DLconfiguration may be replaced with R to configure the following newUL-DL configuration. In the following description, an SF type in theUL-DL configuration is exemplified with order/configuration of [SF #0 toSF #4]+[SF #5 to SF #9]. However, the present invention is not limitedthereto, and SF number/index may be changed (e.g., shifted) whilemaintaining the SF type order. Here, HARQ-ACK transmitting timing for DLdata reception in R may be determined as R present 5 SFs or 10 SFsbefore, and UL grant/PHICH receiving timing configured in the existingreplaced U may be applied without changes to UL data transmission in R.

In this case, similarly to the aforementioned description, differentUL-DL configurations may be combined/mixed with respect to front andrear portions of a radio frame, DL HARQ timing may be based on aspecific UL-DL configuration in which all D, S, or R SF timing aredetermined as D or S, and UL HARQ timing may be based on a specificUL-DL configuration in which all U or R SF timing are determined as U.

0) UL-DL configuration 0-1: [D/S/U/U/R]+[D/S/U/U/R]

1) UL-DL configuration 1-1: [D/S/U/R/D]+[D/S/U/R/D]

2) UL-DL configuration 2-1: [D/S/R/D/D]+[D/S/R/D/D]

3) UL-DL configuration 3-1: [D/S/U/U/R]+[D/D/D/D/D]

4) UL-DL configuration 4-1: [D/S/U/R/D]+[D/D/D/D/D]

5) UL-DL configuration 5-1: [D/S/R/D/D]+[D/D/D/D/D]

6) UL-DL configuration 6-1: [D/S/U/U/R]+[D/S/U/R/D]

As another example, the following UL-DL configuration including only Sand R may be considered. In this case, for example, in order to manage aHARQ process for DL/UL data scheduling and/or corresponding UL-DLconfiguration with respect to S and/or R, an HARQ timing relationship(e.g., 4 [ms or SFs or TTIs] are taken for each of DL grant/DLdata→HARQ-ACK, UL grant→UL data→PHICH) and/or the number (e.g., 8) ofHARQ processes, which are defined/set in a FDD system, may be applied.

7) UL-DL configuration 7: [R/S/R/S/R]+[S/R/S/R/S]

Table 6 below shows the UL-DL configuration 0-1 to 6-1 and UL-DLconfiguration 7. As described above, the present invention is notlimited to Table 6 below, and for example, subframe numbers/indexes maybe independently shifted to generate a new combination while maintainingthe type/order of subframes with respect to each UL-DL configuration.

TABLE 6 Uplink-downlink Subframe number configuration 0 1 2 3 4 5 6 7 89 0-1 D S U U R D S U U R 1-1 D S U R D D S U R D 2-1 D S R D D D S R DD 3-1 D S U U R D D D D D 4-1 D S U R D D D D D D 5-1 D S R D D D D D DD 6-1 D S U U R D S U R D 7 R S R S R S R S R S

The method according to the present invention is not limited to aspecial SF of a TDD NCT, and the principle of the present invention maybe applied in a similar way to a case in which one SF is configured witha similar form (e.g., DwPTS+Tx/Rx switching gap+UpPTS) to a special SFwithout division of FDD/TDD and/or irrespective of a carrier type. Forexample, in a CA situation between different TDD UL-DL configurations, aPcell and a (NCT-based) Scell may be SFs that are differently configuredas a special SF and a DL SF. In this example, when a simultaneoustransceiving operation is not supported/allowed (or based on ahalf-duplex manner), only a (front) portion of a DL SF period of a SCellmay be enabled due to a switching period required by the Pcell.Accordingly, in this example, a DL SF of the corresponding Scell may beconsidered as a shortest S configuration (a DwPTS period of thecorresponding S) and the method according to the present invention maybe extensively thereto in the same/similar way.

Alternatively, when the remaining normal DL period except for a periodset for a special purpose (e.g., MBSFN) in one SF is set to berelatively small (like DwPTS in the special SF), a similar principle tothe proposal according to the present invention may be applied. Arepresentative example of the case corresponds to a SF set as a MBSFN,and the method according to the present invention (e.g., an operation ofOption 1 or 2, and an operation according to E-PDCCH related E-DM-RStransmission/E-CCE mapping and E-PDCCH_startSym, etc.) may beextensively modified and applied to m (e.g., m=2) front OFDM symbolperiods of a corresponding SF except for a period of the correspondingSF, in which a MBSFN signal, i.e., MBSFN data and MBSFN-RS aretransmitted (or configured to be transmitted). In addition, the MBSFNdata may be considered as the same as “DL data in shortest S” and themethod (e.g., an operation according to Option 3, 4, or 5) related tothe present invention may be applied/used. In this case, for example,the MBSFN data may be cross-CC scheduled from a carrier that is not acarrier in which a MBFSN SF for transmitting the corresponding data isset or may be cross-SF scheduled from an (immediately) previous SF thatis not the corresponding MBFSN SF.

An advanced LTE system may reconfigure a specific UL subframe (orspecial subframe), which is previously configured in one TDDcell/carrier, for example, through a system information block (SIB), asa DL subframe or reconfigure the specific UL subframe (or specialsubframe) as a UL subframe. This scheme may be referred to as enhancedinterference management and traffic adaptation (eIMTA). For example,upon receiving information indicating reconfiguration of a specificsubframe as a DL subframe from a UL subframe (or special subframe), anadvanced UE may manage the specific subframe as a DL subframe (or viceversa). The information indicating reconfiguration may besemi-statically or dynamically received through L1 signaling (e.g.,signaling through a PDCCH), L2 signaling (e.g., signaling through a MACmessage), higher layer signaling (e.g., RRC signaling), or the like. Inaddition, for example, reconfiguration of a subframe in a TDD system maybe performed by configuring conversion to a DL subframe from a ULsubframe so as to satisfy a plurality of predetermined UL-DLconfiguration (e.g., Table 1) or reconfiguring the UL-DL configuration.In addition, the specific UL subframe may be reconfigured as a DLsubframe or a special subframe in a FDD call/carrier through the eIMTAscheme.

When the subframe reconfiguration (or the eIMTA scheme) is applied, themethod according to the present invention may be applied. For example,upon receiving the aforementioned information indicating reconfigurationof the subframe, an advanced UE may reconfigure and use a specific ULsubframe as a DL subframe or a special subframe. In this case, thereconfigured special subframe may have a special subframe configuration(e.g., D-only-S, U-only-S, and R subframe) according to the presentinvention. In addition, the advanced UE may operate whileassuming/considering that a collision subframe is configured between aspecific UL subframe prior to reconfiguration and a DL subframe orspecial subframe after reconfiguration. For example, Embodiments 1 to 5or a combination thereof may be applied to the specific UL subframeprior to reconfiguration and the DL subframe or special subframe afterreconfiguration.

In addition, a specific UE may function as an eNB (or relay) throughsystem-to-system communication or device-to-device communication in asystem or a device in which a plurality of cells is connected to a smallcell (e.g., a femto cell and a pico cell) via a backhaul and isaggregated, and thus embodiments (e.g., Embodiments 1 to 5 or acombination thereof) or principles according to the present inventionmay also be applied in the same/similar way to a system in which aplurality of cells is aggregated.

FIG. 17 illustrates a base station and a user equipment to which thepresent invention is applicable.

Referring to FIG. 17, a wireless communication system includes the BS110 and the UE 120. When the wireless communication system includes arelay, the BS 110 or the UE 120 may be replaced with the relay.

The BS 110 includes a processor 112, a memory 114, and a radio frequency(RF) unit 116. The processor 112 may be configured to embody theprocedures and/or methods proposed by the present invention. The memory114 is connected to the processor 112 and stores various pieces ofinformation associated with an operation of the processor 112. The RFunit 116 is connected to the processor 112 and transmits/receives aradio signal. The UE 120 includes a process 122, a memory 124, and an RFunit 126. The processor 122 may be configured to embody the proceduresand/or methods proposed by the present invention. The memory 124 isconnected to the processor 122 and stores various pieces of informationassociated with an operation of the processor 122. The RF unit 126 isconnected to the processor 122 and transmits/receives a radio signal.

The embodiments of the present invention described above arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obvious tothose skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim by asubsequent amendment after the application is filed.

The embodiments of the present invention may be implemented by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware implementation, an embodiment of the presentinvention may be implemented by one or more application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSDPs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), processors, controllers,microcontrollers, microprocessors, etc.

In a firmware or software implementation, an embodiment of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. Software code may be stored in a memory unit and executedby a processor. The memory unit is located at the interior or exteriorof the processor and may transmit and receive data to and from theprocessor via various known means.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a wireless communicationapparatus such as a user equipment (UE), a base station (BS), etc.

The invention claimed is:
 1. A method for communicating with a basestation by a user equipment (UE) operating in half-duplex in a wirelesscommunication system supporting a plurality of carrier types, the methodcomprising: transmitting or receiving a signal to or from the basestation through a first subframe located between a downlink subframe andan uplink subframe in a first cell configured in time division duplex(TDD), wherein when the first cell operates as a first carrier type, thefirst subframe comprises a first downlink period, a first guard period,and a first uplink period, wherein when the first cell operates as asecond carrier type, the first subframe comprises only a second downlinkperiod and a second guard period or comprises only a second uplinkperiod or the second guard period, wherein a length of the second uplinkperiod is increased by a length of the first downlink period as comparedto a length of the first uplink period, and a length of the seconddownlink period is increased by a length of the first uplink period ascompared to a length of the first downlink period, and wherein the firstcarrier type indicates a carrier type in which a cell-common referencesignal is transmitted over an entire system band in all subframes, andthe second carrier type indicates a carrier type in which thecell-common reference signal is transmitted over at least part of thesystem band in some subframes.
 2. The method according to claim 1,wherein, when a second cell is additionally aggregated with the firstcell in the UE, and when a link direction of the first cell and a linkdirection of the second cell are different in an at least partial periodof a time period corresponding to the first subframe, transmission orreception of a signal through the second cell is omitted in the at leastpartial period.
 3. The method according to claim 1, wherein, when asecond cell is additionally aggregated with the first cell in the UE,when the first cell operates as the first carrier type in the firstsubframe, and when the second cell is configured as downlink in an atleast partial period of a time period corresponding to the firstsubframe, a downlink signal is received through the second cell only ina specific period of the time period.
 4. The method according to claim3, wherein the specific period corresponds to the first downlink period,a downlink period configured in the second cell, a downlink periodhaving a shorter length from among the first cell and the second cell,or a downlink period having a smaller number of symbols from among thefirst cell and the second cell.
 5. The method according to claim 1,wherein, when a second cell is additionally aggregated with the firstcell in the UE, when the first cell operates as the first carrier typein the first subframe, and when the second cell is configured as uplinkin a time period corresponding to the first subframe, transmission of aphysical uplink shared channel signal or a physical uplink controlchannel signal through the second cell is omitted in the time period. 6.The method according to claim 1, wherein, when a second cell isadditionally aggregated with the first cell in the UE, when the firstcell operates as the second carrier type and the second cell operates asthe first carrier type in a time period corresponding to the firstsubframe, when the first subframe comprises only the second downlinkperiod and the second guard period, and when the second cell isconfigured as downlink in the time period, detection or reception of aphysical downlink shared channel, a physical downlink control channelmapped over a data region of a subframe, a physical multicast channel,and a positioning reference signal is omitted in the time period.
 7. Themethod according to claim 1, wherein, when a second cell is additionallyaggregated with the first cell in the UE, when the first cell operatesas the second carrier type and the second cell operates as the firstcarrier type in a time period corresponding to the first subframe, whenthe first subframe comprises only the second downlink period and thesecond guard period, and when the second cell is configured as uplink inthe time period, transmission of a physical uplink shared channel and aphysical uplink control channel is omitted in the time period.
 8. A userequipment (UE) operating in a wireless communication system supporting aplurality of carrier types, the UE comprising: a radio frequency (RF)unit; and a processor, that controls the RF unit to: transmit or receivea signal to or from the base station through a first subframe locatedbetween a downlink subframe and an uplink subframe in a first cellconfigured in time division duplex (TDD) through the RF unit, whereinwhen the first cell operates as a first carrier type, the first subframecomprises a first downlink period, a first guard period, and a firstuplink period, wherein when the first cell operates as a second carriertype, the first subframe comprises only a second downlink period and asecond guard period or comprises only a second uplink period or thesecond guard period, wherein a length of the second uplink period isincreased by a length of the first downlink period as compared to alength of the first uplink period, and a length of the second downlinkperiod is increased by a length of the first uplink period as comparedto a length of the first downlink period, and wherein the first carriertype indicates a carrier type in which a cell-common reference signal istransmitted over an entire system band in all subframes, and the secondcarrier type indicates a carrier type in which the cell-common referencesignal is transmitted over at least part of the system band in somesubframes.
 9. The UE according to claim 8, wherein, when a second cellis additionally aggregated with the first cell in the UE, and when alink direction of the first cell and a link direction of the second cellare different in an at least partial period of a time periodcorresponding to the first subframe, the processor further omitstransmission or reception of a signal through the second cell in the atleast partial period.
 10. The UE according to claim 8, wherein, when asecond cell is additionally aggregated with the first cell in the UE,when the first cell operates as the first carrier type in the firstsubframe, and when the second cell is configured as downlink in an atleast partial period of a time period corresponding to the firstsubframe, the processor further controls the RF unit to receive adownlink signal through the second cell only in a specific period of thetime period.
 11. The UE according to claim 8, wherein the specificperiod corresponds to the first downlink period, a downlink periodconfigured in the second cell, a downlink period having a shorter lengthfrom among the first cell and the second cell, or a downlink periodhaving a smaller number of symbols from among the first cell and thesecond cell.
 12. The UE according to claim 8, wherein, when a secondcell is additionally aggregated with the first cell in the UE, when thefirst cell operates as the first carrier type in the first subframe, andwhen the second cell is configured in uplink in a time periodcorresponding to the first subframe, the processor further omitstransmission of a physical uplink shared channel signal or a physicaluplink control channel signal through the second cell in the timeperiod.
 13. The UE according to claim 8, wherein, when a second cell isadditionally aggregated with the first cell in the UE, when the firstcell operates as the second carrier type and the second cell operates asthe first carrier type in a time period corresponding to the firstsubframe, when the first subframe comprises only the second downlinkperiod and the second guard period, and when the second cell isconfigured as downlink in the time period, the processor further omitsdetection or reception of a physical downlink shared channel, a physicaldownlink control channel mapped over a data region of a subframe, aphysical multicast channel, and a positioning reference signal in thetime period.
 14. The UE according to claim 8, wherein, when a secondcell is additionally aggregated with the first cell in the UE, when thefirst cell operates as the second carrier type and the second celloperates as the first carrier type in a time period corresponding to thefirst subframe, when the first subframe comprises only the seconddownlink period and the second guard period, and when the second cell isconfigured in uplink in the time period, the processor further omitstransmission of a physical uplink shared channel and a physical uplinkcontrol channel in the time period.